Redescription of two species and five new species of Dispio Hartman, 1951 (Spionidae: Polychaeta) from the eastern Pacific Coast and Caribbean Sea, with a review of the genus Author Delgado-Blas, Víctor Hugo Author Díaz-Díaz, Oscar text Zootaxa 2016 4178 2 151 181 journal article 10.11646/zootaxa.4178.2.1 0a00d470-cfa7-48f5-9fb3-c11fa79b5f35 1175-5326 163174 C533EE2A-5831-49A2-A4ED-2E7CD94EC663 Dispio panamensis sp. nov. Figure 8 A–Z Material examined. North Pacific , Panama , Naos Island , Punta Culebra , 08º54′47″N , 79º31′46″W , sandy beach, quartz sand (80% fine, 19% medium sand, 1% shell fragments), 0.1 m 2 quadrat, 5 cm deep, 500 µm sieve. Sta. NIB, coll. Deborah M. Dexter, 30 June 1969 , id. Olga Hartman , holotype ( LACM-AHF POLY 6233 ) and paratype ( LACM-AHF POLY 6233 /1). Description. Holotype incomplete, 16.0 mm long, consisting with 43 chaetigers, 1.9 mm wide. Paratype incomplete 10.0 mm long, with 37 chaetigers, 1.0 mm wide. Color in alcohol light brown, no other pigmentation present. Prostomium wedge-shaped, widest subterminally, sharply pointed anteriorly, prostomial tip transparent ( Fig. 8 A), posteriorly tapered, with a short caruncle extending to middle of chaetiger 1, slightly constricted to form a narrow, longitudinal nuchal ridge ( Fig. 8 A, B). Two pairs of small, black, subdermal, kidney-shaped eyes, all eyes arranged in a trapezoid between bases of palps ( Fig. 8 C); or eyes absent ( holotype ) ( Fig. 8 A). Palps lost. Peristomium long ( Fig. 8 A–C), expanded laterally, partially enveloping prostomium and extending around base of palps, forming moderate lateral wings ( Fig. 8 A–C), separated from chaetiger 1. All notopodial postchaetal lamellae almost completely fused to branchiae, but with free and pointed tips. Notopodial postchaetal lamellae of chaetigers 1–2 shifted dorsally and deeply serrated ( Fig. 8 C). Lamellae of chaetiger 1 bearing 5–8 digitiform lobes along margin (arranged in pairs) ( Fig. 8 C); notopodial lamellae of chaetiger 2 with 5–7 digitiform lobes along middle and distal margins (comb-shaped) ( Fig. 8 C) basal margin wider and rounded; lamellae of chaetiger 3 with 2–3 digitiform papillae at distal end; lamellae with ruffled margin below papillae, basal margin rounded ( Fig. 8 B, D); lamellae of subsequent chaetigers with ruffled distal margin, basal margin large, wider, rounded ( Fig. 8 E) ( holotype : chaetigers 5 (right), 7 (left) with 1–3 small digitiform papillae at distal end; lamellae with ruffled margin below papillae, basal margin rounded); around chaetigers 7–11 margin ruffled giving lamellae bilobed appearance ( Fig. 8 F); and to end of fragment becoming notched ( Fig. 8 G) between distal and middle margins; basal margin large, wider, rounded, distal lobe with pointed tip; around chaetigers 28– 30 ventral edge (lobe) of lamellae gradually becoming triangular ( Fig. 8 H); ventral edge pointed on chaetigers 27– 42 ( 42 in holotype ) ( Fig. 8 H–J). Ventral and dorsal edges of notopodial and neuropodial lamellae overlapping from chaetigers 4–7 ( 4 in holotype ) ( Fig. 8 E–F) to end of fragments ( Fig. 8 J). Notopodial prechaetal lamellae larger, oval on chaetigers 1–10 ( Fig. 8 B, F–H), subsequently decreasing in size and becoming rounded on middle and posterior chaetigers ( Fig. 8 I–J); not basally fused with notopodial postchaetal lamellae. Each segment with a pair of dorsal C-shaped double bands of cilia with a transverse band of cilia between them ( Fig. 8 K). Lateral organs between notopodial and neuropodial postchaetal lamellae absent. Neuropodial postchaetal lamellae of chaetigers 1–2 serrated, shifted to dorsal side; neuropodial lamellae of chaetiger 1 with 4/2 ( 4 in holotype ) digitiform lobes along margin ( Fig. 8 B); neuropodial lamellae of chaetigers 2 with 5/2–0/2 (holotype- paratype , respectively) digitiform lobes ( Fig. 8 B, E); chaetiger 3 with 0–1 ( 1 in holotype ) digitiform lobes ( Fig. 8 B, D–E); lamellae of chaetigers 4–6 smooth and rounded ( Fig. 8 E); subsequent lamellae becoming wider, rectangular, with rounded edges from chaetigers 7–12 ( Fig. 8 F), subsequently becoming much wider with dorsal lobe rounded ( Fig. 8 G) forming blunt, elongated upper border ( Fig. 8 H) from around chaetigers 27–31 ( 31 in holotype ), a pointed upper border on chaetiger 38 ( Fig. 8 I), and then blunt again up to end of fragments ( Fig. 8 J). Neuropodial prechaetal lamellae moderate, rounded on anterior chaetigers ( Fig. 8 B), larger, oval on middle chaetigers ( Fig. 8 F), progressively decreasing in size on subsequent chaetigers ( Fig. 8 I–J); all lamellae not basally fused with neuropodial postchaetal lamellae. Branchiae present from chaetiger 1, continuing to end of fragments; all branchiae long, smooth, tapered ( Fig. 8 F–G), overlapping each other on anterior chaetigers; almost completely fused to notopodial postchaetal lamellae; branchial tips free, distally pointed on anterior chaetigers ( Fig. 8 B, F–G); distal inner edge bulky giving appearance of a spearhead ( Fig. 8 F, G, K) on middle and posterior fragments; branchiae longer than notopodial lamellae ( Fig. 8 F, K). Each branchia with a dense band of cilia along inner edge ( Fig. 8 G, K). Accessory branchiae present from chaetigers 9/ 14 in the holotype and 8/ 9 in the paratype , initially as a simple long digitate lobe that arises from dorsolateral side of body behind notopodial base; number of lobes gradually increasing to 5 or 6 in posterior chaetigers, arranged in one row (palmate-shaped) ( Fig. 8 I). Notochaetae of chaetiger 1 arranged in a dorsal tuft and a ventral fascicle; dorsal tuft with 40–50 long, slender, smooth, alimbate capillaries extending beyond margins of notopodial lamellae ( Fig. 8 A–B) between palps; ventral fascicle arranged in two rows: an anterior row of short, wider unilimbated, slightly granulated, pointed capillaries ( Fig. 8 L), and a posterior row of slender, smooth, unilimbated, capillaries, longer than those of first row; less numerous than those of dorsal fascicle. Notochaetae of chaetiger 2 arranged in same manner as on chaetiger 1, except that dorsal tuft has only about 5, shorter, pointed, unilimbated dorsal capillaries, capillaries in anterior row Characters Prostomial shape; NoPoL: A. B. C. D. E.: Notopođial anđ AnNePoL: A. B. NePoL becoming the Branchial structure caruncle 1. Chaet. 1 neuropođial Smooth margin, shapeđ: pointeđ upper borđer a. Overlapping each FIGURE 8. Dispio panamensis sp. nov. Holotype (LACM-AHF POLY -6233; A, B, D–Z; paratype LACM-AHF POLY -6233/ 1): C): (A) anterior region, dorsal view; (B) anterior region, lateral view; (C) anterior region, dorsal view; (D) parapodium of chaetiger 3; (E) parapodium of chaetigers 1–6; (F) parapodium of chaetigers 7–14; (G) parapodium of chaetiger 32; (H) parapodium of chaetigers 27–31; (I) parapodium of chaetiger 38; (J) parapodium of posterior chaetiger; (K) middle segment, dorsal view; (L) notopodial chaeta of anterior row on chaetiger 1; (M) notopodial chaeta of anterior row on chaetiger 2; (N) notopodial chaeta of anterior row on chaetiger 7; (O) notopodial chaeta of posterior row on chaetiger 32; (P) posterior notopodial chaeta of anterior row; (Q) posterior notopodial chaeta of posterior row; (R) dorsal tuft chaetae of notopodial chaeta on posterior chaetiger; (S) anterior neuropodial chaeta of anterior row; (T) anterior neuropodial chaeta of posterior row; (U) ventral chaeta located in the position of the sabre chaeta of anterior chaetiger; (V, V’) anterior neuropodial chaeta of anterior row (dorsal position, ventral position); (W) sabre chaeta of chaetiger 32; (X) neuropodial hooded hook; (Y) neuropodial chaeta of posterior row on chaetiger 32; (Z) posterior neuropodial chaeta. CBC= C-shaped double band of cilia. Scale bars: A–H 1.0 mm; I–J 0.2 mm; K–M 0.5 mm; N–R, V–Z 0.01 mm; S–U 0.005 mm. TABLE 1. Some taxonomic characteristics of Dispio species. NoPoL= Notopođial postchaetal lamellae; AnNePoL= Anterior neuropođial postchaetal lamellae; NePoL= Neuropođial postchaetal lamellae; A. Serrateđ (No. papillae), B. Entire with ruffleđ margin, C. Entire smooth, D. With a notch, E. Appearance bilobeđ, “?” đenotes absence of information. 2. Chaet. 2 lamellae with 1. Chaet. 1 from Chaetigers: other on anterior 3. Chaet. 3 eđges overlapping 2. Chaet. 2 chaetigers 4. Chaet. 4 or touching 3. Chaet. 3 b. Fuseđ to notopođial 5. Chaet. 5 4. Chaet. 4 lamellae 6. Chaet. 6 5. Chaet. 5 c. Branchial tip shape 7. Chaet. 7 8. Chaet. 8 9. Chaet. 9 10. Chaet. 10 11. Chaet. 11 . uncinata Hartman , Spinđle-shapeđ, pointeđ 1. A (5 – 6) No 1. A (5) Arounđ 31 a. No 10. C

1951 anteriorly with curveđ tip 2. A (5 – 8)	2. A (4)	b. Partially
đistally, with a pair of 3. A (1), B lateral emarginations; 4. B narrow anđ long 5. B 6. B	3. A (4) 4. B, rounđeđ 5. B, rounđeđ	c. Distally pointeđ on all chaetigers
7. B 8. B 9. B

11. C ……continued on the next page Characters Prostomial shape; NoPoL: A. B. C. D. E.: Notopođial anđ AnNePoL: A. B. NePoL becoming the Branchial structure

D. magnus (Day, 1955) Fusiform , bluntly 1. B	Overlapping on 1. B, rounđeđ?	a. No
pointeđ anteriorly; 2. B narrow anđ long 3. B 4. B 5. B 6. B	posterior chaetigers 2. B, rounđeđ 3. B, rounđeđ 4. B, rounđeđ 5. B, rounđeđ	b. Completely on anterior chaetigers, with free tips on posterior ones c. Distally blunteđ on
7. B 8. B 9. B 10. B	anterior chaetigers
11. B
D. maroroi Gibbs, 1971 Peanut-shapeđ, pointeđ 1. A (7) anteriorly; long, narrow, 2. A (5)	No 1. B, rounđeđ 20 – 40 2. B, rounđeđ	a. Yes, touching on miđđle chaetigers
large 3. B 4. B 5. B 6. B	3. B, rounđeđ 4. B, rounđeđ 5. B, rounđeđ	b. Partially c. Distally pointeđ in spear-shape on all chaetigers
7. B 8. B 9. B
10. B 11. B

TABLE 1. (Continueđ) caruncle 1. Chaet. 1 neuropođial Smooth margin, shapeđ: pointeđ upper borđer a. Overlapping each 2. Chaet. 2 lamellae with 1. Chaet. 1 from Chaetigers: other on anterior 3. Chaet. 3 eđges overlapping 2. Chaet. 2 chaetigers 9. C

4. Chaet. 4 5. Chaet. 5 6. Chaet. 6 7. Chaet. 7 8. Chaet. 8 9. Chaet. 9 10. Chaet. 10 11. Chaet. 11	or touching	3. Chaet. 3 b. Fuseđ to notopođial 4. Chaet. 4 lamellae 5. Chaet. 5 c. Branchial tip shape
D. glabrilamellata Fusiform , sharply 1. C Blake & Kuđenov, 1978 pointeđ anteriorly; long 2.C anđ narrow 3. C 4. C 5. C 6. C 7. C 8. C	No	1. B, rounđeđ? – 35 (Fig. 10đ, Blake & a.? 2. B, subrectangular Kuđenov, 1978) b. Partially 3. B, subrectangular c. Distally pointeđ on 4. B, subrectangular all chaetigers 5. B, subrectangular
9. C 10. C
11. C
D. brachychaeta Blake, Fusiform , pointeđ 1. C 1983 anteriorly; short 2.C 3. C 4. C 5. C 6. C 7. C 8. C	No	1. B, rounđeđ? – 70 (Fig 5C, Blake, a.? 2. B, rounđeđ 1983) b. Completely in 3. B, rounđeđ anterior chaetigers, free 4. B, rounđeđ on chaet. 20 5. B, rounđeđ c. Distally blunteđ on posterior chaetigers

10. C 11. C oculata Imajima, Fusiform , sharply 1. C, slenđer Overlapping on 1. B, rounđeđ? – 40 enlargeđ ( Fig. 3 g, a.? pointeđ anteriorly; long 2. C, with obtuse tips posterior chaetigers 2. B, rounđeđ Imajima, 1990 ) b. Completely, forming anđ blunt 3. C, strap-like 3. B, rounđeđ strap-like structure; free 4. C 4. B, rounđeđ from chaet. 36 – 38 5. C 5. B, rounđeđ c. Distal tips club- 6. C shapeđ, granulateđ on 7. C miđđle anđ posterior 8. C chaetigers 9. C 10. C 11. C ……continued on the next page Characters Prostomial shape; NoPoL: A. B. C. D. E.: Notopođial anđ AnNePoL: A. B. NePoL becoming the Branchial structure caruncle 1. Chaet. 1 neuropođial Smooth margin, shapeđ: pointeđ upper borđer a. Overlapping each TABLE 1. (Continueđ) 2. Chaet. 2 lamellae with 1. Chaet. 1 from Chaetigers: other on anterior 3. Chaet. 3 eđges overlapping 2. Chaet. 2 chaetigers 4. Chaet. 4 or touching 3. Chaet. 3 b. Fuseđ to notopođial 5. Chaet. 5 4. Chaet. 4 lamellae 6. Chaet. 6 5. Chaet. 5 c. Branchial tip shape 7. Chaet. 7 8. Chaet. 8 9. Chaet. 9 10. Chaet. 10 11. Chaet. 11 . latilamella Williams, Ovoiđ shapeđ, pointeđ 1. A, spoon-shapeđ (2 – 8) No 1. B, rounđeđ 30 – 33 ( Fig. 5 H, a. No 2007 anteriorly; short anđ 2. A (?) 2. B, rounđeđ Williams, 2007 ) b. Partially blunt 3. A (?) 3. B, rounđeđ c. Distally pointeđ on 4. A (?) 4. B, rounđeđ all chaetigers 5. A (?) 5. B, rounđeđ 6. A (?) 7. A (?) 8. A (?) 9. A (?) 10. A (?) 11. A (?) 12. A (?) 13. A (?) . anauncinata sp nov. Peanut-shapeđ, pointeđ 1. A (2 – 6/1 – 5) Overlapping on 1. A (2/1) 37 – 39 a. No anteriorly; short anđ 2. A (1 – 3/0 – 2) miđđle anđ 2. A (1) b. Partially blunt 3. B posterior chaetigers 3. B. rounđeđ c. Distally pointeđ on 4. B 4. B. rounđeđ all chaetigers 5. B 5. B. rounđeđ 6. B 7. B 8. B 9. B 10. B 11. B . bescanzae sp nov. Hourglass-shapeđ, 1. A (4 – 9) Overlapping on 1. A (3 – 5) 29 – 40 a. No bluntly pointeđ 2. A (8 – 11) posterior chaetigers 2. A (3 – 5) b. Partially anteriorly; long anđ 3. A (8 – 10) 3. A (3 – 5) c. Distally pointeđ on triangular 4. A (8 – 10) 4. A (4), B, rounđeđ all chaetigers 5. A (8-10) 5. B, rounđeđ 6. A (8 – 10) 7. A (1 – 8) 8. A (5), B 9. A (5), B 10. A (5), B 11. B 12. B ……continued on the next page Characters Prostomial shape; NoPoL: A. B. C. D. E.: Notopođial anđ AnNePoL: A. B. NePoL becoming the Branchial structure TABLE 1. (Continueđ) caruncle 1. Chaet. 1 neuropođial Smooth margin, shapeđ: pointeđ upper borđer a. Overlapping each 2. Chaet. 2 lamellae with 1. Chaet. 1 from Chaetigers: other on anterior 3. Chaet. 3 eđges overlapping 2. Chaet. 2 chaetigers 4. Chaet. 4 or touching 3. Chaet. 3 b. Fuseđ to notopođial 5. Chaet. 5 4. Chaet. 4 lamellae 6. Chaet. 6 5. Chaet. 5 c. Branchial tip shape 7. Chaet. 7 8. Chaet. 8 9. Chaet. 9 10. Chaet. 10 11. Chaet. 11 lenislamellata sp. Peanut-shapeđ, sharply 1. C No 1. B, triangular 30 – 34 a. Yes, after chaet. 3 . pointeđ anteriorly; short, 2. C 2. B, subtriangular b. Partially narrow, large 3. C 3. B, rounđeđ c. Distally pointeđ on 4. C 4. B, rounđeđ all chaetigers, 5. C 5. B, rounđeđ 6. C 7. C 8. C 9. C 10. C 11. C longibranchiata sp Rectangular-shapeđ, with 1. A (1 – 3/2 – 5) No 1. B, triangular 30 – 36 a. Yes, also on miđđle . a short, đistal conical tip; 2. B 2. B, subtriangular chaetigers short, blunt anđ swollen 3. B 3. B, subtriangular b. Partially 4. B 4. B, rounđeđ c. Distally pointeđ on 5. B 5. B, rounđeđ all chaetigers 6. B 7. B 8. B 9. B 10. B 11. B all narrow panamensis sp. nov. Weđge-shapeđ, sharply 1. A (5 – 8) Overlapping on 1. A (4/2) 27 – 38 a. Yes pointeđ anteriorly; short, 2. A (5 – 7) anterior anđ miđđle 2. A (5/2 – 0/2) b. Partially narrow, slightly 3. A (2 – 3) chaetigers 3. A (0 – 1) c. Distal inner eđge constricteđ 4. B 4. B bulky giving the 5. B, A (right: 1) 5. B appearance of 6. B 6. B spearheađ on miđđle 7. B, A (left: 3) anđ posterior fragments 8. E 9. E 10. E 11. E ……continued on the next page wider unilimbated, pointed, reticulated, and slightly striated in basal region of shaft ( Fig. 8 M), capillaries in posterior row smooth, pointed, unilimbated; capillaries less numerous in tuft than in rows. Arrangement of chaetae on subsequent chaetigers is similar to that of chaetiger 2, with dorsal tuft chaetae decreasing gradually in size and number (2 or 3 at most) up to about chaetiger 13, chaetae of anterior row wider, unilimbated, limbation decreases halfway up shaft ( Fig. 8 N), capillaries in posterior row long, smooth, unilimbate in middle and at distal end ( Fig. 8 O); posterior notochaetae arranged similarly in anterior and middle chaetigers, except that chaetae in anterior row wider, reticulated, and less unilimbated (with reduced limbation) ( Fig. 8 P), and in posterior row, slender, smooth, wider, longer, unilimbated ( Fig. 8 Q); dorsal chaetae smooth, long, alimbate distally with long, pointed tips ( Fig. 8 R). Notopodial hooded hooks absent.

TABLE 1. (Continueđ) Characters	Accessory branchial pairs a. Begin on chaetigers: b. No. of lobes	Notochaetae of chaetiger 1 a. Anterior row b. Posterior row	Ventral chaetae locateđ in the position of the sabre chaetae of chaet. 2 anđ subsequent chaetigers	Neuropođial hoođeđ hooks a. Begin on chaetigers: b. Main hoođ	Pygiđium
D. uncinata Hartman, 1951	a. 14 – 16 b. 6 – 8	a. Stout heavily reticulateđ, granulateđ, bilimbateđ capillaries b. Granulateđ, alimbateđ capillary	2 – 3 capillaries longer, stout, heavily reticulateđ, granulateđ, alimbateđ, all chaetae with long pointeđ tips	a. 25 – 27 b. Distally entire, the hoođ extenđs đistally up to, or slightly beyonđ, the apex	Tapers građually to a short, narrow collar with a slight miđđorsal notch anđ a posterior aperture; without flange or cirrus
D. magnus (Day, 1955) D. maroroi Gibbs, 1971 D. glabrilamellata Blake & Kuđenov, 1978	Absent a. 18 – 20 b. 6 – 8 a. 23 b. 4 – 6	a.?, granulateđ, bilimbateđ capillaries b. Granulateđ bilimbateđ capillary a. Heavily reticulateđ, unilimbateđ, pointeđ capillaries b. Smooth, alimbateđ capillaries a. Reticulateđ capillaries b. Smooth capillaries	Smooth, but becoming granulateđ, unilimbateđ on chaetiger 14 3 longer, stouter slightly reticular, granulateđ, unilimbateđ Smooth from chaet. 9 – 11, but becoming thicker anđ transversely barređ from arounđ chaet. 25	a. 44 b. Distally open a. 28 – 29 b. Distally open a. 22 – 26 b. Distally open	No anal cirri??
D. brachychaeta Blake, 1983	Absent	a. Heavily granulateđ, reticulateđ, unilimbateđ capillaries b. Smooth capillaries	4 – 6 unilimbate, granulateđ at đistal enđ of shaft	a. 32 b. Hooks with tight hoođs, frequently peeling off from shaft	?
D. oculata Imajima, 1990 D. latilamella Williams, 2007	Absent a. 19 b. 1 – 6	a.? b.? a.? b.?	Elongate, curveđ, limbation wiđe, heavily reticulateđ anđ granulateđ c. 2H3,?	a. 27 – 33 b. Open a. 19 b. Open	? Ređuceđ, with small papillae on ventral surface
D. anauncinata sp nov.	a. 11 – 21 b. 1 – 5	a. Smooth, alimbateđ capillaries b. Smooth, alimbateđ capillaries	2 – 3 longer, stouter heavily reticulateđ, granulateđ, unilimbateđ capillaries	a. 17 – 25 b. Distally open, the shaft almost straight	Miđventral flap (đarkbrown pigment), anđ two pairs of long cirri.
D. bescanzae sp nov. D. lenislamellata sp. nov.	a. 13 – 30 b. 1 – 7 a. 11 – 21 b. 3 – 5	a. Stout mođerate reticulateđ, granulateđ, unilimbateđ capillaries b. Smooth, alimbateđ capillary a. Slightly reticulateđ, granulateđ, slenđer, unilimbateđ capillary b. Smooth, unilimbateđ capillary	Long, reticulateđ, slightly granulateđ, alimbateđ capillaries; except on chaet. 10 – 15, where longer, stouter, heavily reticulateđ 2 longer, stouter, heavily reticulateđ, granulateđ, slightly unilimbateđ capillaries	a. 22 – 27 b. Distally entire, the hoođ extenđs đistally up to, or slightly beyonđ the apex a. 15 – 21 b. Distally entire, hoođ extenđs đistally	Miđventral flap anđ a pair of long cirri Miđventral flap anđ a pair of cirri
D. longibranchiata sp nov.	a. 12 b. 2 – 5	a. Smooth, slenđer, alimbateđ capillaries b. Smooth, alimbateđ capillaries	2-3 longer, stouter heavily reticulateđ, granulateđ, unilimbateđ capillaries	a. 22 – 24 b. Distally open	?
D. panamensis sp. nov.	a. 9/14H8/9 b. 5 – 6	a. Slightly granulateđ, unilimbateđ, pointeđ capillaries b. Smooth, unilimbateđ capillary	6 short, slenđer, reticulateđ, granulateđ, unilimbateđ capillaries, except on chaet. 11 – 12 where longer, stouter, pointeđ, unilimbateđ	a. 21 – 32 b. Open đistally open	?

Neurochaetae of chaetiger 1 arranged in two rows of about 20 slender chaetae: anterior row comprised of slightly granulated, reticulated, unilimbate capillaries ( Fig. 8 S), and posterior row of long, pointed, smooth, slightly unilimbate capillary chaetae ( Fig. 8 T), anterior capillaries shorter than posterior ones; in addition, a ventral tuft of four slender, shorter, smooth, pointed, slightly unilimbated capillaries ( Fig. 8 U) located in position of sabre chaetae; arrangement of neurochaetae on chaetiger 2 and subsequent chaetigers similar to that of chaetiger 1, except that capillaries in anterior row stout, heavily granulated, reticulated, unilimbate (dorsal capillaries with wider sheaths ( Fig. 8 V) than ventral ones ( Fig. 8 V ′), ventral capillaries less reticulated and striated in base of shaft ( Fig. 8 V ′), and those in posterior row long, smooth, slightly unilimbate capillary chaetae; ventral tuft with six short, slender, reticulated, granulated, unilimbated sabre chaetae; chaetae longer, stouter, heavily reticulated, granulated, pointed, unilimbated from chaetigers 11–12, ( Fig. 8 W), decreasing in number to 2–3 chaetae per fascicle. Unidentate neuropodial hooded hooks ( Fig. 8 X) replacing anterior row of capillary neurochaetae from chaetigers 21–32, up to eight per neuropodium, posterior row slightly granulated, wider, unilimbated, shaft striated basally ( Fig. 8 Y); on posterior chaetigers, posterior row with smooth, bilimbated, slender chaetae slightly striated along shaft ( Fig. 8 Z). Hooded hooks opened distally, slightly curved ( Fig. 8 X). Pygidium lost. Remarks. Dispio panamensis sp. nov. is closely related to D. uncinata in that the lengths of the peristomium and lateral wings are the same, and the first three notopodial and neuropodial lamellae are deeply serrated with digitiform papillae. Dispio panamensis sp. nov. is also similar to D. anauncinata sp. nov. , in having the first two notopodial and neuropodial lamellae deeply serrated with digitiform papillae. However, D. panamensis sp. nov. can be distinguished from D. uncinata in that the former has a wedge-shaped prostomium that is widest subterminally, sharply pointed anteriorly and without a pair of lateral emarginations; a shorter caruncle, a longer peristomium, the notopodial lamellae of chaetiger 8 and subsequent chaetigers have a bilobed appearance, the branchiae overlap each other on anterior chaetigers, the branchial tips have a bulky distal inner edge giving the appearance of a spearhead on the middle and posterior fragments, and other differences are provided in the Table 1 and key. For differences between D. panamensis sp. nov. and D. anauncinata sp. nov. and D . bescanzae sp. nov. see remarks of D. anauncinata and D . bescanzae sp. nov. The differences between this new species and the other species examined in this study are provided in the key and Table 1 . Ecology. Sandy beach, quartz sand (80% fine, 19% medium sand, 1% shell fragments). Type locality. North Pacific , Naos Island , Punta Culebra , Panama . Etymology. The species name is derived from the country of Panamá and the suffix indicates that it is found in that region.