222 CllETACEOUS PELEOYPODA 



this peculiar form from any other known. The concentric striae are very distinct, 

 especially on the strong convexity near the umbones ; they are less so in the middle, 

 but become again more strongly marked near the periphery. The radiating ribs 

 are numerous, close together, and also traceable on the internal surface of the 

 shell. 



Locality, — Monglepaudy and Ootatoor, in a grey calcareous sandstone ; appa- 

 rently a rare shell. 



Formation, — Ootatoor group. 



ERAGUM, Bolten, 1798 (vide p. 210). 



\/ 1. EiiAGUM PEJi^cuRiiENS, Stoliczka, PI. XI, Eigs. 1-2. 



Frag, testa oblique suh-quadrangtilari^ suh-cordata, solida, umhonibus latiusciilis, 

 prominulis, valde incurvis, sub-medianis, antice angustatim rotundata^ infra lente 

 convexa^ postice rectiuscide ac oblique truncata ; in superficie costis 35-45 radi- 

 antibus sub-cBqualibus^ siUcis profundis angustissimis disjunctis, ornata ; costis anticis 

 ac lateralibus, seu medianis, in junioribus speciminibiis lamellose-, in adultis sub- 

 rotundate- tuberculosis, iis in declivitate postica sitis distantioribus et sub-lcevigatis ; 

 lumila angusta, IcBvigata ; f uteris crassis, prominulis ; margine interno crasse 

 dentato ; cardine dentibus cardinalibus et lateralibus sicut in speciminibus typicis 

 instructo ; impressione palliali postice conspicue truncata seu lente sinuata. 



Height of shell : its length ... ... ... 0*80 



Thickness „ : . „ ... ... ... 0-70 



This is a typical species of the sub-genus Fragum, which has scarcely been 

 known before from cretaceous rocks. The form is longer and less high than most 

 of the recent species, and the radiating ribs are hardly tuberculated at all on the 

 posteriar declivity ; the shell close belovv^^ the posterior muscular impression is 

 strongly thickened and the pallial line is truncated or slightly sinuated posteriorly ; 

 in every other respect it agrees wdth the type species of the above genus. 



Locality, — In calcareous sandstone north of Odium and west of Anapaudy; 

 at the last named locality chiefly small specimens, but in very large numbers, occur. 

 They are extremely like a little species which lives at present very abundantly 

 on the coral reefs of the Nicobar islands, and apparently never grows to a large 

 size. 



Formation. — Ootatoor group. 



