220 CEETACEOUS PELEOYPODA 



respect with each other, and whatever slight variations there are to be observed in 

 the coarseness of the concentric or radiating ribs they are common to both. 



Localities. — Gamdamungalum^ Serdamnngalum, Alundanapooram, Anapaudy, 

 &c. ; very common; either in a bluish calcareous sandstone or more frequently 

 occurring in a brownish earthy limestone, sometimes passing into a conglome- 

 ratic rock. 



Formation, — Trichinopoly group. 



In Europe the species is found almost everywhere in Cenomanien, Turonien, 

 and Senonien deposits, particularly, however, in the middle series. It is also re- 

 corded by Prof. E. Komer from Texas, but the figure given of one of the specimens 

 would, I think, indicate a different species with the anterior (especially the lower) 

 edge shorter and the ribs more distant. 



/ 

 v' 2. Peotocahbium delicatulxjm, Stoliczha, PL XIII, Eig. 8. 



Frot, testa tceniolata, suh-orUciilata, moderate convexa, postice suh-truncata, 

 nmhombus prominentibus^ lateraliter compressis ; superficie concentrice lente striata, 

 postice radiatim multi-costulata. 



Height of shell : its length .. . ... ... ... ... 1-02 



Thickness „ : „ ... (approximately) ... 0-68 



This species is closely allied to Trot, hillanum, but is decidedly higher, with 

 more prominent umbones, more numerous ribs on the posterior declivity and alto- 

 gether of a thinner structure. 



iomfeVy.— Shutamungalum, in a light grey sandstone, apparently belonging 

 to the upper series of the cretaceous deposits. 



Formation, — ? Arrialoor group. 



3. Peotocaedium Pondicheeiense, d'OrUgny, PL XII, Eigs. 4-7. 



1847. Cardium Ponticeriense, d'Orb., Voyage Astrolabe, &c., Palseont., pi. 5, figs. 21-22. 



Frot, testa sub-trigonata, moderate inflata, crassa, paulo altiore quam longa, 

 siib'cequilaterali, sub-recta; umbonibus valde prominentibus, lateraliter compressis, 

 inctirvis instructa, antice ac infra ad marginem lente rotundata, postice oblique trun- 

 cata, vix producta ; superficie costis concentricis crassis, rotundatis in declivitate 

 antica scEpissime sub-obsoletis notata ; declivitate postica costis 20-24 radiantihus paulo 

 prominulis confertim tecta, ad marginem interiorem denticulata, Cardo dentibus 

 crassis sicut in speciehus typicis instructus. 



Height of shell : its length ... ... .... ... i-02 



Thickness „ : „ ... .,, _^^ Q.gg 



As to form this species is intermediate between Frot, hillanum and Frot, 

 altum, being more regularly triangular and less high than the latter; the concentric 



