472 CRETACEOUS PELECYPODA 



costata ; nmhone depresso, obtnso, sccpe indistincto ; area ligament, lata, medio vix 

 excaoata ; impress, muse, excenlrica, prope marfjincm ventralem sita, plus mimisve ab 

 innbone remota, late semi-ocata ; imp. palliali undique crasse plicata, sub-marginali. 



A more or less elongated or largely ovate species with unequal valves, the 

 lower attached valve hciug principally characterized by the strongly produced and 

 occasionally somewhat twisted umbo, and both by the numerous strong concentric 

 plications and the crenulated, sub-marginal pallial impression. The lower valve 

 has, as noted by Gold fuss, indistinct radiating ribs, generally obsolete at the sides 

 of the valve ; the upper valve is only marked with concentric striae or plications, 

 and its umbo is always obtuse and truncated, the apex being sometimes also 

 slightly bent towards the ventral side. The muscular scars are generally of a 

 broadly semi-ovate shape, placed rather near the ventral margin, but sometimes 

 nearer to, sometimes more remote from, the beaks. 



LocaUties. — Near Arrialoor, Authicoodicaud, Olapaudy, &c. ; in whitish sand- 

 stone. 



Formation. — Arrialoor group. 



Ost. aciitirostris is found in Europe in the upper cretaceous beds (Santonien 

 of Coquand) ; it has been recorded from variovis parts of France, from near 

 Brighton in England, from Maastricht and Aachen, from Sweden, from Galicia, 

 and it also occurs in the same beds in Algiers. 



9. OsTREA Telugensis, StoUczka, PI. XLIX, Pigs. S— 4; PI. L, Pigs. 1—2. 



Ost. testa irregulariter suh-rotimdata, valvis sub-csqttalibus, deplanatis, varie 



flexis, antice angustatim productis, superficie concentrice lamellosis et striatic, 



lamellis phis mimisve distantibus, ad marginem accumulatis ; nmboiiibiis obtusatis, 



tii/midulis ; area Ugamentali lata, medio excavata ; impress, muse, semi-circiilari, 



aliqiian to excenlrica . 



The valves are sub-equal and flattened, roundish, with the ventral side some- 

 what narrowly produced ; the surface is only marked with somewhat distant 

 lamellcE of growth ; the beaks are obtuse, internally with a large ligamental area, 

 excavated in the middle of both valves, but, as usually, more so in the lower than 

 in the upper valve. The muscular scars are large, nearly semi-circular, excentric, 

 placed somewhat nearer to the ventral tban to the dorsal side. 



LocaUtg. — Near Comarapolliam, in a light coloured calcareous sandstone and 

 in a conglomerate. 



Formation. — Arrialoor group. 



Tbis species closely resembles Coquand's Ost. Fasiphae (Monog. Ostr. eret., 

 18G9, p. 173), differing from it by the ventral margin being more produced, and the 

 concentric lamellae apparently coarser and more distant from each other. 



