OF SOUTHERN INDIA. 173 



of the type of Cyth. gigantea, appears to support the suggestion of their helonging 

 to distinct sub-genera. 



Locality. — South of Garudamungalum, iu a brownish calcai'eous sandstone 

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



Formation. — Trichinopoly group. 



6. Cytherea [Callista] sctjlpturata, Stoliczka, PI. VII, Figs. 7-9. 



Cyth. testa ovata, antice rotnndata, postice sub-tnincata ; declicitate lunula re 

 paululiim concava, areale convexitiscida, crassa, injlexa, supra marginibus obttmns- 

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

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

 convexitisculis, concentrice liratis, liris crassis sulcis prqfundis angustisque separatis, 

 prope umbones obsoletis ; umbonibus approximatis paululum antice versus incurvis, 

 acutis. Cardo in valva sinistra dentibus tribus cardinalibus, sub-cequalibus et unico 

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

 pallii ? 



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



Height : length ... ... ... ... 0-74 



Thickness : height ... ... ... ... O'CO 



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

 and represented by the well known C. 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 eqvially 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 Callistce already represented during the cretaceous period in the same 

 regions where the recent forms occur. A very similar form also occurs in the 

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

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

 gressive periods of time. 



Locality. — Neighbourhood of Kunanore, in a conglomeratic sandstone. 



Formation. — Arrialoor group. 



2u 



