44 "^ CEETACEOUS PELECYPODA 



2. ConBULA PABSTJRA, Stoliczha, PI. I, Figs. 23-21, and P]. XVI, Figs. 3-1. 



C. testa suh-quadrangiilari, alia, postice hianle ; valvula dextra multo major e 

 quam sinistra, inoiqiiilaterali, convexa, umbone ohtuso, prominulo et incurvo instructu, 

 antice sub-rotundata, postice trnncala, hreviter caudata, ad marginem elevata, in 

 snperjicie concentrice crassc costulata ; valvula sinistra ovulala, dextrd multo minori, 

 a)itice rotundata, jiostice anrjustata atque ohlns'msoida, in snperficie fere lievi, wnbone 

 leviter incurvo, acutulo; cardlne dentibus ac fossls, sicut in Corbiilis typicis, inslruclo. 



Height of the nt,'ht valve : its length ... ... ... 083 



„ 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, subcauclate posteriorly, and con- 

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

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

 resembles a Jij/a, 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 measm-es 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. CoRBULA MINIMA, d'Orbifjny, PI. I, Figs. 19-22, and PI. XVI, Figs. 7-12. 



1847. C. minima, d'Orb., Pal. de la voy. Astrolabe et Zelee, pi. 5, fig.s. 18-19. 



C. testa oblonga, sub-eqiiilaterali, antice ac piostice snbangulata, clansa, umbo7iibus 

 pro»iinn,Us, fere medianis, antice versus inciirvis, S2tperficie striis minntis indttla ; 

 valoa dextra paulo majori quam sinistra, in utraque carina acutiiiscnla ab umbone 

 ad terminationem posteriorem decurrente instructa. 



Height of shell (pi. 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 fi'ont ; both are 

 equally finely and concentrically striated, and a sharp cai'ina 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 1 m.m., Avhich was the greatest size observed among many specimens. 



