352 CRETACEOUS PELECYPODA 



4-5 nhliquis el 5 postlcis eloucjatis fere hovizontalihus et parallelis instructus, omtiinis 

 in laleribiis supcrioribus ac infcriuril)ns minute striolatis ; morgine interno antero- 

 ventrali pUcatim dentato. 



Height of shell : its length ... ... ... ... 0-83 



Thickness „ : „ ... ... ... ... 079 



This species differs by its greater height in proportion to its length, by the 

 narrower area and more strongly bent anterior hinge-teeth, from 3Iac. japelictim ; 

 it is to all appearance the species -which has been figured by d'Orbigny under the 

 name of Area disparilis, which can appropriately be retained for it. The difference 

 in the ribbing of the two valves is similar to that noticed iu the previous species, 

 but the ribs themselves are not so strong as in that species. 



Locality. — Near Alundanapooram, in a light coloured calcareous sandstone. 



Formation. — Trichinopoly group. 



TEIGOXOAP.CA, Conrad, 1867, (see p. 337). 



1. Trigonoarca telijgensis, Stoliezka, PI. XIX, Fig. 1. 



Trig, testa sub-quadrangulari, moderate injlata, postice ab nmbone valde cari- 

 nata et ad marginem sub-oblique truncata ; timbone valvce sinistrce obtusiuscido, s'uU 

 cato, breviter inciirvo ; snperficie costulis radiantibus, striis tenuioribus concentricis 

 decussatis, in declivitate postica sub-ohsoletis, in anticu sub-spimdosis ornata ; area 

 angustissima, angulatim bistriata ; cardo dentibus phiribus divaricatis, exterioribus 

 paulo longioribus, instructus. 



Height of shell nearly equal to its length. 



Thickness „ : its length ... ... ,,, ... 0'78 



Only a single valve of this rare species has as yet been found, but it is charac- 

 teristically different from any other cretaceous species. It is not much inflated, 

 posteriorly strongly carinated, very broadly truncate, and possesses a very narrow 

 lio-amental area. The fine concentric strise form on the radiating ribs little 

 tubercles, which are almost spimilose on the anterior side of the shell. The hinge- 

 teeth are the same as in other species of Trigonoarca. 



Locality. — North of Alundanapooram, in a brownish highly calcareous sand- 

 stone. 



Formation. — Trichinopoly group. 



2. Trigonoarca abrtjpta, Forbes, PI. XIX, Figs. 4-5. 



1846. Area ahriipta, Forbes, Trans. Geol. Soc, Lond., vii, p. 149, pi. xiv, fig. 2; — eadem auctonim. 



Trig, testa magna, sub-trigonata, suh-cequilaterali, antice valde p7'oducta, ad 

 marginem sub-rotundata, postice acute carinata, deinde abrupte declivi et oblique 

 snb-truncata, iimbonibus lotis, proniincntibns, incurvis ; superficie striis, costulifornii* 

 bus, radiantibus, alteris parum tenuioribus concentricis decussatis, notata ; margine 



