472 CEETACEOUS PELECTPODA 



costata ; umbone depresso, obtuso^ scepe indistincto ; area ligament, lata, medio vix 

 excavata ; impress, muse, excentrica, prope marginem ventralem sita, plus minusve ah 

 umbone remota, late semi-ovata ; vmp, palliali undique crasse plicata, sub-marginali. 



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

 lower attached valve being 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 Goldfuss, 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. 



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

 stone. 



Formation, — Arrialoor group. 



Ost, acutirostris is found in Europe in the upper cretaceous beds (Santonien 

 of Coquand) ; it has been recorded from various 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, StoUczM, PL XLIX, Pigs. 3—4; PL L, Pigs. 1—2. 



Ost, testa irregulariter suh-rotundata, valvis suh-cequalibus, deplanatis, varie 



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



lamellis plus minusve distantibus, ad marginem accumulatis ; umbonibus obtusatis, 



twmidulis; area ligamentali lata, medio excavata; impress, muse, semi-circulari, 



aliquanto excentrica. 



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

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

 lamellae 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 than to the dorsal side. 



Locality,— ^^^-^ OomarapoUiam, in a light coloured calcareous sandstone and 

 in a conglomerate. 



Formation, — Arrialoor group. 



This species closely resembles Coquand's Ost, Fasiphae (Monog. Ostr. cret , 

 1869, p. 173), differing from it by the ventral margin being more produced, and the 

 concentric lamellae apparently coarser and more distant from each other. 



