352 CEETACEOUS PELECTPODA 



4-5 obliquis et 5 posticis elongatis fere liorizontalibus et parallelis instructus^ omninis 

 in lateribus siiperioribus ac inferioribus minute striolatis ; margine interna antero- 

 ventrali pUcatim dentato. 



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



Thickness „ : „ ... ,.. ... ... 0*79 



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

 narrower area and more strongly bent anterior hinge-teeth, from Mac. japeticum ; 

 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 diflPerence 

 in the ribbing of the two valves is similar to that noticed in 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. 



TEIGONOARCA, Conrad, 1867, (see p. 337). 



1. Teigonoarca telugensis, StoliczJca, PL XIX, Eig. 1. 



Trig, testa siih-quadrangtilari, moderate inflata, postice ah umbone valde cari" 

 nata et ad marginem sub-oblique truncata ; umbone valvce sinistrce obtusiusculo, sul- 

 cato, breviter incurvo ; superficie costidis radiantibus, striis tenuioribus concentricis 

 decussatis, in declivitate postica sub-obsoletis, in antica sub-spinulosis ornata ; area 

 angustissima, angulatim bist?'iata; cardo dentibus pluribus divaricatis, ea^terioiHbus 

 paulo longioribus, instructus. 



Height of shell nearly equal to its length. 



Thickness „ : its length ... ... ... ... Q-ys 



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 

 ligamental area. The fine concentric striae form on the radiating ribs little 

 tubercles, which are almost spinulose 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. Trigonoauca abeupta, Forbes, PL XIX, Eigs. 4-5. 



1846. Area ahrtipta, Forbes, Trans. Geol. Soc., Lond., vii, p. 149, pi. xiv, fig. 2 \~eadem auctorum. 



Trig, testa magna, sub-trigonata, sub-cequilaterali, antice valde producta, ad 

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

 sub'truncata, umbonibus latis, prominentibus, incitrvis ; superficie striis, costuliformi^ 

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



