OE SOUTHEEN INDIA. 173 



of the type of Cyth, gigantea^ appears to support the suggestion of their belonging 

 to distinct sub-genera. 



Locality, — South of Garudamungalum, in a brownish calcareous sandstone 

 full of little shells ; only the figured left valve has as yet been found. 



Formation. — Trichinopoly group. 



/ 6. Cytheeea [Callista] sculpturata, Stoliczka, PL VII, Eigs. 7-9. 



CytJi, testa ovata, antice rotundata^ postice suh-truncata ; declivitate lunulare 

 paululum concava^ areale convexiuscula, crassa, inflexa^ supra marginihus ohtusms- 

 culis instructa ; lunula elongata angusta, medio paulo elevata, antice acuta^ tinea 

 impressa marginata ; margine ventrale moderate ac uniforme curvato ; valvis moderate 

 convexiuscidis, concentrice liratis, liris crassis sulcis profundis angustisque separatis, 

 prope umhones ohsoletis ; umbonihus approximatis paululum antice versus incurms, 

 ucutis. Cardo in valva sinistra dentibus tribus cardinalibus, sub-csqualibus et unico 

 elongato lunulare instructus ; fulcris tenuibus sub margine areale obtiiso sitis ; sinu 

 pallii ? 



Length of largest specimen ... ... ... .., 50 m. m. 



Height : length ... ... ... ,., 074 



Thickness : height ... ... ... ... 0*60 



This species belongs to a type of Callistce, mostly peculiar to the eastern seas, 

 and represented by the well known (7. erycina, Linn., which occurs already in the 

 miocene deposits of Europe, and is one of the commonest species on the eastern 

 coast of Ceylon. As compared with this species the form of our fossil is shorter, 

 the concentric ribs are less flattened, though almost equally strong in both species, 

 and the interspaces narrow and deep ; towards the umbones the ribs become obso- 

 lete. The area is deep and externally margined by elevated obtusely rounded edges ; 

 the fulcra are rather thin and deeply situated. In other respects the Trichinopoly 

 fossil does not offer any peculiarities. It is extremely interesting to find this 

 type of Callist(s already represented during the cretaceous period in the same 

 regions where the recent forms occur. A very similar form also occm^s in the 

 tertiary deposits of Burma. Such instances cannot fail to be of the greatest 

 importance in tracing out the geographical distribution of animal life during pro- 

 gressive periods of time, 



ioca/^^J/3— Neighbourhood of Kunanore, in a conglomeratic sandstone. 

 Formation, — Arrialoor group. 



2 IT 



