OF SOUTHERN INDIA. 81 



height, the upper and lower sub-parallel margins, and the moderate convexity of the 

 valves are the most striking distinctions of this shell as compared with other known 

 PholadomycB, of which some tertiary species, like Ph. Alpina and rectidorsata, have 

 the greatest resemblance to the Indian fossil. On the well preserved surface 

 of the shell the ribbings are less distinctly perceptible than on the cast. 



Localities, — Not uncommon in sandstone beds at Garudamungalum, Serda- 

 mungalum, and north of Alundanapooram. 



Formation, — Trichinopoly group. 



4. Pholadomya pedisulcata, Stoliczka, PL IV, Pig. 1, and PL XVI, Pig. 26. 



PA. testa perlonga, sub-cylindracea, valde incequilaterali, parte antica hrevi, pavlo 

 infiata^ radiatim multisulcata, ad terminationem Jiiante ; super ficie concentrice 

 anguste sulcata^ et minute striata ac interdum in parte mediana nonnullis costis sub- 

 ohsoletis notata^ terminatione postica suh-truncata^ Jiiante, sensim comp)resslusGula, 



H eight of shell : its length ... ... ... ... 0'4i5 



Thickness „ : „ ... ... ... ,„ 0'41 



This is a remarkable type of a Pholadomya, quite distinct from any that have as 

 yet been described. It is very long, considerably inflated, and towards the posterior 

 end greatly compressed. The short anterior part is inflated, separated from the rest 

 by a deep sulcus running somewhat obliquely from the front edge of the beak to the 

 lower margin ; it is provided with numerous and rather sharp radiating ribs, which 

 form undulations at the small anterior gape ; besides that there are in some specimens 

 on the middle portion of the surface a few distant and rather indistinct ribs. The 

 beaks are broad, not much elevated, but strongly incurved and almost touching each 

 other. The lower edge of the shell is very slightly convex and the upper posterior 

 slightly concave. 



Localities . — In bluish calcareous sandstone near Garudamungalum and in 

 brownish sandstone beds near Anapaudy. 



Formation, — Trichinopoly group. 



VI, Family,— SAXICA VIDJE, 



The animals have, like the Anatinidm, the mantle margins united, with a 

 small opening in front for the purpose of protruding a small digitiform foot ; the 

 siphons are united in their entire length, sometimes separated at their terminations ; 

 there are two pairs of gills on each side of the body, being occasionally slightly 

 prolonged in the branchial siphon. The palpi are, as usually, triangular and striated ; 

 the arrangements of the other organs are identical with those of typical MTACFA, 



The shells are of an elongated ovate form, usually inequilateral and equivalve ; 

 they are thick, externally highly calcareous, and internally sometimes perlaceou^, 

 covered with an epidermis, which extends over the siphons, and in some respect 



w 



