OF SOUTHERN INDIA. ' 199 



and with thick lamellar ridges ornamented only in front, while on either side of 

 the carina the sm-face is smooth. The lunula is helow margined by a double 

 impressed line ; the area is rather flattened ; the nymphte not prominent. 



Locality. — Arrialoor, in a light grey sandstone. 



Formation. — Arrialoor group. 



CICATREA, Stoliczka, (vide p. 192). 



3. Cypeina [cicatrea] cordialis, Stoliczka, PL X, Fig. 1. 



Cyp. [Cleat.'] testa elongata, valde injlata, nmbonibus valde prominentibus et 

 incurvis instructa, postice attenuata, carina acutissima ab umbonibus ad terminationem 

 iwstero-inferiorem decurrente, in superjicie costuUs Icevigatis crassinscnlis concentricis 

 ornata; regione stipero-postica eminenter cordiformi, moderate convexa ; lunula 

 cordata, linea impressa marginata ; ligamentum in duabus furcis paidulum divergen- 

 tibus, lamina crassa testacea separatis et postice breviter prolongatis, situm. 



Height : length of shell ... ... ... _ Q.g2 



Thickness : „ „ ... ... Q.yj^ 



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



This beautiful species is distinguished by a very high and sharp ridge runnino- 

 from the beaks to the postero-inferior end, giving the shell when viewed per- 

 pendicularly towards the supero-posterior (fig. lb), or towards the antero-inferior 

 region, an eminently heart-shaped outline. The surface is marked with concentric 

 distant ribs, which are especially distant near the beaks, these being strongly 

 prominent, incurved, and somewhat distant from each other. The ligament is, as 

 already stated, lodged in a double groove ; the lunula is cordate, obtusely pointed 

 below and margined by an impressed line. The left valve has three cardinal teeth, 

 the posterior one being very thin, laminar, the two anterior are triangular and 

 very strong, the base of the median being united with the top of the anterior 

 by a low rib ; a distinct rib is seen in front of the anterior muscular impression, 

 it has the appearance of an anterior lateral tooth, but Las in reality nothing 

 to do with the hinge-teeth. Of the right valve I observed distinctly only the 

 two anterior cardinal teeth being almost confluent into one. On a cast specimen 

 the muscular impressions are very much elevated ; they must be, therefore, deeply 

 excavated on the shell, which is remarkably thick. 



I have already alluded to d'Orhignj's Isocardia pyrenaica and I. galiciana, 

 Alth., which are the only cretaceous species bearing some resemblance to this 

 interesting fossil. 



Localities. — Serdamungalum and Koloture, in a light coloured sandstone ; rare. 



Formation. — Trichinopoly group. 



