OF SOUTHERN INDIA. 197 



sinistra dente postico tenui, hreviori, antico elongato, sub-Jlexuoso, et in utraque voIku 

 dente laterali postico moderato instructiis. 



Height : length of shell ... ... ... varj-ing from 0'85 - 0'92 



Thickness : „ „ ... ... , 090- 100 



Length of largest specimen ... ... . . . 80 m. m. 



This species has its nearest ally in Zittel's Cyprina 'yVenilicardla\ crassidcntata 

 from the Gosaii formation, but our shell is always shorter and more tumid than the 

 European species, in Tvhich also the posterior cardinal tooth of the right valve is 

 more distinctly bifid. The thickness of the shell varies considerably, (as shown on 

 plate viii) ; an obtuse indistinct ridge runs from the beaks to the j)ostero-inferior 

 end ; the lunula is roundish or broadly oval, surrounded by an impressed line ; the 

 beaks are strongly incurved, rather close together, only in old very inflated speci- 

 mens distinctly curved outward with their points. The surface of the shell 

 exhibits striae of growth, some of which are, especially nearer to the periphery, 

 stronger and more closely placed than in the centre. The valves close perfectly 

 without leaving any posterior gape. The fulcra and the hinge-teeth are remarkably 

 ro])ust. 



Localities. — Koloture, Serdamungalum, Alundanapooram, Comarapolliam, 

 Arrialoor, Vylapaudy, Olapaudy, &c., &c. 



Furmations. — Trichinopoly (the three first named localities) and Arrialoor 

 groups ; rather rare in the former, but common in the latter. 



CYPRINA, Lam., 1812, (vide p. 191). 



1. Cyprina Eorbesiana, Stoliczka, PL IX, Figs. 2-8. 



Cyp. testa ovato-elongata, plus mimisve tumida, carina acuta ab timbonihiis 

 ad terminationem infero-posteriorcm decurrente instructa, in superjicie distanter 

 crasse lamellose costata ac striata, antice ad peripheriam rotundata, infra patihdum 

 jlexuosa, siibrecta, supra ac postice fere uniforme convexiuscula ; umbonibus valde 

 pi'ominentibtts, incurvis, approximatis ; nymphis crassis ; area angustata, longa, ad 

 medium elevata ; lumda transversaliter ovato-elongata, infra profundiusctda et tinea 

 impressa marginata ; cardo dentibiis tribus cardinalibus et uno postico laterali in 

 utraque valva iis Cyprinarum typicarum persimilihus instructus. 



Height : length of shell... ... ... varying from 073 - 0'86 



Thickness : „ „ ... ... ... „ ., 0-55 - 083 



Length of largest specimen ... ... ... 75 m. m. 



Shell elongately ovate, more or less tumid, according to which the proportions 

 of height to the length vary ; beaks strongly incurved, close together, a rather sharp 

 ridge running from them to the infero-posterior end, which is somewhat attenuated, 

 being less high than the front part ; the surface is covered with more or less 

 distant, lamellar, concentric ribs, between which some thinner strise are to be 



3b 



