A unique radiation of marine littorinid snails in the freshwater streams of the Western Ghats of India: the genus Cremnoconchus W. T. Blanford, 1869 (Gastropoda: Littorinidae) Author Reid, David G. Author Aravind, Neelavara Ananthram Author Madhyastha, Neelavara Ananthram text Zoological Journal of the Linnean Society 2013 2013-01-18 167 1 93 135 http://dx.doi.org/10.1111/j.1096-3642.2012.00875.x journal article 10.1111/j.1096-3642.2012.00875.x 0024-4082 5292273 CREMNOCONCHUS GLOBULUS SP. NOV. (FIGS 2E, 4F, 5K, L, 8, 11H–L, 12H–L, 13A, B) Types: Holotype ZSI / WGRS /IR.INV-2310 (Fig. 11I, J); 2 paratypes ZSI / WGRS /IR.INV-2311, 2312 (Fig. 11K); Lesser Kadambi Falls , Chikmagalur Dist. , Karnataka , India ( 13.24384°N , 75.17056°E ). Etymology: Latin globulus , globular, in reference to shell shape. Diagnosis: Shell globular, without ribs; pseudumbilicus moderate, sometimes perforated; surface with satin sheen, no microstriae. Operculum weakly calcified, no internal ridge. Penis with lateral glandular flange, slender filament. Western Karnataka State . Shell ( Figs 4F , 11H–L): Shell H 6.0– 8.8 mm . Shape ( Table 1 ) globular; whorls rounded, without angulation; suture impressed; apex eroded; base slightly swollen. Columella moderately narrow, wider at base. Pseudumbilicus moderate (to 0.8 mm ), sometimes perforated, outlined by angled margin, sometimes forming a slight rounded rib. Surface almost always without ribs above periphery; rarely a slight thickening or indistinct rib near suture. Surface with satin sheen; spiral striae almost or entirely absent ( Fig. 4F ). Diameter of first whorl 0.50–0.66 mm ( N = 3). Colour: dark brown or olive-brown, sometimes darker on spire and in band at suture; columella and umbilicus purple-brown; aperture pale brown to whitish, with sutural band showing through. Animal: Head, tentacles, and sides of foot pale grey to black, tentacles darker, paler at tip of snout. Gills: up to 40 leaflets; black. Operculum ( Table 1 ; Fig. 5K, L): opercular ratio 0.364 –0.421 ; weakly calcified, dark red-brown, no internal ridge. Penis ( Fig. 12H–L ): unpigmented or slightly pigmented; base wrinkled, with long thickened flange running across left side towards eye, glandular knob on right side, and slight glandular swelling distally (sometimes opaque); invagination about half length of base in ethanol-fixed specimens; filament slender, rarely protruding in ethanol-fixed specimens. Pallial oviduct: as for genus. Radula ( Fig. 13A, B ): Relative radula length 2.66– 3.43. Rachidian: length/width 1.10–1.22; 5 cusps (+ 1 outer denticle on either side). Lateral: 5 cusps (+ 1 inner denticle). Inner marginal: 5 cusps. Outer marginal: 4–5 cusps. Major cusp of each of 5 central teeth triangular leaf-shaped with pointed to slightly rounded tip; other cusps pointed. Range ( Fig. 8 ): Western Karnataka State , Kudremukh ( 55 km north-east of Mangalore ). Records (see Supporting Table S1 ): Karnataka State : Lesser Kadambi Falls (ZSI/WGRS/IR.INV-2310, 2311, 2312); Greater Kadambi Falls (ZSI/WGRS/IR.INV-2308, 2309). Habitat and ecology: Common in film of water flowing over rock face beside waterfall (Fig. 2E); on stones in shallow streams (to 30 cm deep) with fast-flowing water; in partial shade of riparian vegetation in wet evergreen forest. Altitude 941 and 967 m . Remarks: Four Cremnoconchus species have similar umbilicate, globular to turbinate, smooth shells ( Table 4 ). Cremnoconchus globulus is distinguished by its lack of a basal rib (present in C. cingulatus ), moderate pseudumbilicus and weakly calcified operculum (well calcified in C. castanea ). Distinction from C. hanumani , with which it occurs in the same microhabitat, is discussed in the Remarks on that species. The penes of all four are diagnostic ( Figs 12 , 14, 15).