Taxonomy and distribution of irregular echinoids (Echinoidea: Irregularia) from Sri Lanka Author Arachchige, Gayashan M. Author Jayakody, Sevvandi Author Mooi, Rich Author Kroh, Andreas text Zootaxa 2019 2019-01-03 4541 1 1 100 journal article 27715 10.11646/zootaxa.4541.1.1 9c3fecf1-4e11-4c79-a908-e0a5abbaf3ca 1175-5326 2617460 B11E734C-218B-418C-84E6-719AB3C58AFF Clypeaster reticulatus (Linnaeus, 1758) Figures 22–24 1758 Echinus reticulatus Linnaeus : p. 666. 1948b Clypeaster ( Rhaphidoclypus ) reticulatus (Linnaeus) .—Mortensen: p. 71–76; pl. 18: figs. 1–21; pl. 26: fig. 3; pl. 65: figs. 2, 13, 16. Material studied. Two denuded specimens: WUSL/EI/19 from Hiriketiya and WUSL/EI/20 from Nilwella, Sri Lanka . Description. Shape and size —Small, 35 and 41 mm TL; test elongate ovoid to pentagonal, distinctly longer than broad, TW 75% and 76% TL; test low, 26% and 31% TL in height; test margin greatly thickened, forming a distinct ring-shaped depression between margin and petalodium; aboral side slightly raised toward apex, concave on oral side, infundibulum deep, bowl-shaped, c. 14% TL and 17% TL. Apical system —Monobasal; situated slightly anterior of centre on aboral surface, c. 45% and 48% TL from anterior margin; circular gonopore in each interambulacrum near madreporic plate; ocular pores small and indistinct. Ambulacra —Petaloid area 63% and 65% TL; petals inflated, closed distally; petal III longest, c. 32% TL; anterior paired petals c. 23% TL, considerably shorter than other petals; posterior paired petals c. 30% TL; paired petals broader distally than other petals; interporiferous zone conspicuously elevated, consisting of 5–6 primary tubercles along widest part of petals; furrow connecting pores in each pore pair deep and sharply delimited; 2–5 primary tubercles between furrows; oral ambulacra simple, inconspicuous food groves present along axis of each ambulacrum. Interambulacra —All interambulacra on oral surface disjunct; on aboral surface, small, shallow pits present in corners of sutures ( Fig. 23 , A); primary tubercles less dense on oral surface than aborally. Tuberculation —Primary tubercles perforate, areoles sunken, dense miliary tuberculation in between primary tubercles; oral side with adoral region of much smaller tubercles; largest tubercles present toward test edge, intermediate sized tubercles present very close to peristome, smallest tubercles present in between zone of largest tubercles and zone of intermediate-sized tubercles ( Fig. 23 , B). Peristome —Round to subpentagonal, small, width c. 7% TL, located close to centre, c. 46% and 51% TL from anterior margin. Periproct —Round to transverse oval, length 4% and 5% TL, width 4% and 6% TL; significantly smaller than peristome, c. 64% of peristome length; situated close to posterior edge of test, c. 4% TL away from posterior margin. Internal buttressing —Pillars inside test more abundant along midlines of interambulacra; marginal buttressing largely absent ( Fig. 23 , C). Geographic range. Indo-West Pacific, from Islands of West Indian Ocean ( Clark 1925a ), Mauritius (de Loriol 1883 ), East Africa & Madagascar ( Brown 1910a ), Red Sea ( Agassiz 1872 ), South East Arabia ( Mortensen 1948c ), Persian Gulf ( Mortensen 1940 ), West Indian & Pakistan ( Koehler 1922 ), Maldives area ( Koehler 1922 ), Sri Lanka ( Herdman et al. 1904 ; Koehler 1922 ), Bay of Bengal ( Koehler 1922 ), North Australia ( Clark 1925a ) and East Indies (de Meijere 1904 ; Mortensen 1948a ) to Philippine Islands ( Mortensen 1948e ; Mooi & Munguia 2014 ), China & South Japan ( Clark 1925a ), South Pacific Islands ( Clark 1954 ) and Hawaiian Islands ( Clark 1925b ). Bathymetric range. Littoral zone to 125 m ( Mooi & Munguia 2014 ). Observed occurrence in Sri Lanka . On the beach of Hiriketiya Bay and Nilwella along the southern coast of Sri Lanka ( Fig. 24 ), in biogenic sand; first recorded in Sri Lanka by Herdman et al. (1904) . Bathymetric range in Sri Lanka 0–100 m . Remarks. C. reticulatus can be distinguished easily from C. humilis by having a greatly thickened test margin that forms a distinct ring-shaped depression between the margin and petaloid area. The oral surface of C. reticulatus is strongly concave, making a bowl-shaped infundibulum. Primary spine tubercles decrease in size towards the peristome, then increase again adjacent to the peristome.