144 



Records of the Indian Museum. [Vol. XXII, 



Remarks. — This species alons; with other species of the group 

 are distinguished b3' their somewhat elongate, comparatively 

 narrow and rather compressed shells. C. ceylonica is characterized 

 by the rather large and sinuous anterior border, broadly truncate 

 and elongate posterior border and the forwardly recurved um 

 bones ; the hinge of this species is also very different from that of 

 the other Indian species. 



Cyrena galatheae Morch. 

 Plate XX, figs. 14—17. 



1915. Cyrena galatheae. Preston, Faun. Brit. Ind. Freshtv.-Moll .. p. 

 '207. 



I give below a detailed description of the shell of this species 

 as the original description by Morch is not quite complete. 



Shell very large, solid, thick, greatly swollen in the upper 

 third, compressed below, roughly trigonal, much longer than high, 

 very inequilateral with the umbones situated much nearer to 

 the anterior than the posterior edge, with a yellowish brown to 

 blackish epidermis with regular concentric striae, growth-regions 

 not distinctly marked ; anterior margin much shorter tnan the 

 posterior, somewhat concave in the upper region or just next to 

 the umbones, then after a short straight course curving in to form 

 the podium ; posterior margin in its proximal part only slightly 

 curved, but rapidly descending downwards, further part straight 

 owing to the truncate nature of the region next to the gonium, 

 with an obtuse angle between the straight lower and the si ghtly 

 curved upper region ; ventral border only slightly arched ; um- 

 bones prominent, greatly eroded in adult shells, in 3'oung shells 

 recurved forwards and inwards but not meeting eac . other in 

 the middle line, and sculptured with closely situated concentric 

 striae, with a broad but shallow lunule, carinated in the mid- 

 dle ; ligament long, thick and prominent. Hinge as in the genus 

 but greatly curved and rather forwardly placed owing to the posi- 

 tion of the umbones, with the lateral teeth more compact and 

 solid, the upper pair of laterals in the right valve reduced to 

 small thickenings only ; cardinals very slanting and strong. 



Measurements (in millimetres). 



Length 

 Height 

 Thickness 



h. 



h 



104 98 120 

 92 82 I 106 

 52 51 I 75 



Specimens a 

 Lawrence Island, 

 and h — / from the Nicobars. 



The specimens from various 



-c are from the Andaman Islands, d from John 

 e from Kondul Island, /, g, from Trinkat Island 



localities differ to some extent 



