M CEETACEOUS PELECYPODA 



^J 2. CoRBULA PAIISUEA5 StoUczka, PL I, Figs. 23-24, and PL XVI, Pigs. 3-4. 



C testa sub-quadrangulari, alta, postice Mante ; valvula dextra multo majors 

 quam sinistra^ incequilaterali, convexa, umbone obtuso, prominulo et incurvo instructa, 

 antice sub-rotundata, postice truncata^ breviter caudata, ad marginem elevata, in 

 superficie coficentrice crasse costulata ; valvula sinistra oviilata^ dextra multo minori, 

 antice rotundata, postice angustata atque obtusiuscula, in superficie fere Icevi, umbone 

 leviter incurvo^ acutulo; cardine dentibus ac fossis^ sicut in Corbulis typicis^ instructo. 



Height of the right valve : its length ... ... ... 0"83 



„ of the shell : „ ... ... ... 0-58 



The two valves of this species are remarkably unlike each other in size and 

 ornamentation, the right being much the larger, subcaudate posteriorly, and con- 

 centrically strongly ribbed ; the left is very small, slightly convex, tightly fitting 

 in the other, and nearly smooth. Viewed from the right valve the shell greatly 

 resembles a Mya^ indicating a wide posterior gape. The right valve has, as usual, 

 a deep cartilage-pit and one large tooth in front of it, the left valve a posterior 

 cartilage process and an anterior pit. The posterior muscular impression is in the 

 right valve rounded, large ; the pallial impression very slightly insinuated. 



The largest specimen observed measures 6 m.m., but it seems rarely to grow 

 to that size. 



Locality, — In bluish highly calcareous shelly sandstone at Garudamungalum, 



Formation, — Trichinopoly group. 



^ 3. CoBBTJLA MINIMA, d'OrUguy, PL I, Pigs. 19-22, and PL XVI, Pigs. 7-12, 



1847. C. minima, d'Orh., Pal. de la voy. Astrolabe et Zelee, pi. 5, figs. 18-19. 



(7. testa oblonga, sub-equilaterali, antice ac postice subangulata^ clausa^ umionibus 

 prominulis, fere medianis, antice versus incurvis, superficie striis minutis induta ; 

 valva dextra paulo majoin quam sinistra, in utraque carina acutiuscula ab umbone 

 ad terminationem posteriorem decurrente instructa. 



Height of shell (pL xvi, fig. 7) : its length ... ... ... 0'68 



Thickness „ ... : „ ... ... ... 0*51 



The valves are in this species subequal, the right one being a little larger than 

 the left, the umbones are subcentral, and incurved towards the front; both are 

 equally finely and concentrically striated, and a sharp carina runs from the 

 umbones towards the posterior end, which is somewhat produced and attenuated ; 

 from the carina the shell slopes to the postero-superior margin ; both valves are 

 perfectly closed at their terminations. The hinge is identical with that of recent 

 Corbulce, the tooth in the right valve and the process in the left being, as compared 

 with the size of the shell, rather small. The species rarely seems to grow larger 

 than 4 m.m., which was the greatest size observed among many specimens. 



