OF SOUTHERN IXDIA. 317 



5. Trigonia semiculta, Forbes, PL XV, Figs. 19, 22, 23, 27. 



1846. Triffouia semiculta, Forbes, Trans. Geol. Soc, Lond., rii, p. 1.51, pi. xviii, fig. 9. 



1847. „ sinuafa, Park., apud d'Orb., \oy. Astrol., Paleont., pi. iv, figs. 29-30 — non eadeni Parkinson. 

 1850. „ semiculta, Forbes, apud d'Orb., Prod. II, p. 240; — eadem auctorum. 



T. testa elongate sitb-quadmngidart, hicequUatemli, moderate compressa, verticihus 

 ohtusis pavvuUs instructa, antice et infra rotiindata, posttce producta, ad termina- 

 tionem late truncata, area paulo convexiuscula, latisslma, elongate trigonali, Icevigata, 

 in junioribus speciminibiis supra longittidinaUter sub-sulcata atque pone vertices trans- 

 versaliter costulata; superficie cetera concentrice miilticostata, costis Icevigatis, ohtusis, 

 fere cequidistantibus, antice paulo deflexis et usque ad marginem continuis. 



Tliis species is readily recognised from tlie previous by the anterior termina- 

 tion of the concentric ribs, which are bent somewhat downwards and extend 

 up to the extreme margin. It is a more compressed and posteriorly more 

 produced shell than T. orientalis ; young specimens are, however, very closely 

 allied, and the anterior termination of the ribs becomes the sole distin2"uishin<i: 

 character. 



This is no doubt the species which d'Orbigny first identified with the European 

 T. sinuata of Parkinson, and both are indeed very closely allied to each other, 

 the only difi'erence being that the Indian shell has a somewhat wider, smooth area, 

 and that it is posteriorly truncated, instead of being gradually narrower and 

 terminally rounded, as seen in the various figures of sinuata. I have no speci- 

 mens of this last to compare, but should that character prove not to be constant, 

 I would without much hesitation consider both shells as belonging to the same 

 species. D'Orbigny's figure in the Voy. d' Astrolabe appears to be an enlarged 

 one of a young specimen, but I was unable to trace out the original in the ' Jardiu 

 des plantes' collection. In the Prodrome, (II, p. 210,) d'Orbigny wrongly identi- 

 fies simiata from Pondicherry with suborbicularis, Forbes, retaining the last one 

 as distinct from orientalis, Forb. This is a double mistake, as already pointed out. 



Another species allied to semiculta was described by Conrad as T. syriaca from 

 Palsestine. Fraas pronounces it to be the same as T. sinuata, Park. 



Locality. — Neighbourhood of Anapaudy and north-east of Maithal, in a com- 

 pact calcareous, and in soft, sandstone ; rare. 



Formations. — Trichinopoly group. 



6. Trigonia minuta, StoUczka, PI. XV, Figs. 18, 20, 21. 



T. testa parva, elongato sub-trigonata, valde incequilaterali, regione ab apice 

 ad marginem postero-inferiorem decurrente obtuse angidata, postice producta, 

 attenuata et ad terminationem angustatim truncata; margine lunulari et areali fere 

 rectis, angulum 105° ad apices formantibus ; lumda angusta, elongata paululum 

 excavata, area perlonga, ang^ista, fere plana, an/babus Uvvigatis ; superficie costuUs 



