458 CRETACEOUS PELECYPODA 



Menard)j MUnsteri, Hag.^ ostracinaj^ Lam., ^ = haliotoidea, Sclilotli., = cormi-arietis ^ Nilss,, 

 ^= stomatoidea, Forbes), pliciferaj Duj._, PuscIiiij-\ Coq., retictdata, Gein., sigmoidea, Reuss, 

 SolUeri, Coq., sqiiamula^ Reuss, striato-costata, Eichw., Tamnlka^ StoL, Texana^% Roem., 

 TrautscJioldij Coq., ( = contorta, Eichw. ex^artejy Washingtoni, Coq., (=^][iarasitica,t^ Gabb). 



EXOGYRA, Say, 1821, (see p. 454). 



1. ExoGYRA HALIOTOIDEA, Sowerby, PI. XXXVI, Pig. 7, and PL XXXVII, 



Pigs. 1-3. 



1813. Chama haliotoidea, Sow., Min. Concli., i, p. Q7, pi. 2^.—Gri/p7i(Ba, Exogyra, aut Ostrea eadem 



auctorum. 

 1846. Bxogyra orientalis, Forbes, Trans. Geol. Soc, Lond., vii, p. 156, pi. xiv, fig. 6. 

 1869. Osti^ea lucifer, Coquand, Monog. Ostr. cret., p. 43. 



^a:, testa late semiovata, auriforme, depressa, sub-lcevigata, ad marginem dor- 

 salem convexa, ad ventralem rectiuscula ; valva affixa planulata, nonnunquam irregu- 

 lariter excavata, ad marginem convexum subcarinata, deinde rapide declivi, umbone 

 valde intortOi valva libera fere plana, ad marginem convexum aliquantum incrassata, 

 umbone indistincto ; fovea ligamentali longa, marginali, infra costa elevate marginata ; 

 impressione musculari subcentrali, magna, elongate ovata, 



Porbes already noticed the great similarity of Lis IE, orientalis to the 

 European JE, haliotoidea, pointing out that the difference consists in the angle of the 

 larger valve being more marginal, while in the European it is more median. This 

 character is, however, not constant, either in the European or in the Indian form. 

 I can see no essential diflPerence between most of our specimens and those originally 

 figured by Sowerby (loc. cit.). The form of both the valves is almost exactly 

 the same, even applying to some peculiar rugosities along the ventral margin. 

 Specimens in which the angle of the larger valve is more median (see pi. xxxvii, 

 fig. 2,) also occur in South India, but they are rare, while in Europe the same 

 are of more common occurrence. Sometimes the form of the shell is nearly roundly 

 ovate, or the larger valve is almost gibbose and rough on the surface. 



D'Orbigny (Prod, ii, p. 256,) considered the present species, or rather Porbes' 

 JE. orientalis, as identical with his E, stomatoidea = E. ostracina, which identifica- 

 tion is of course inadmissible. Coquand's newly proposed specific name lucifer 

 also becomes obsolete. 



Locality. — Ootatoor, in a grey or reddish calcareous sandstone. 



Formation, — Ootatoor group. 



I], haliotoidea has been found in the Upper Greensand of England, at various 

 localities in Prance, Germany, Bohemia, Sweden, &c. ; it is a characteristic fossil 

 of the middle series of cretaceous deposits, (Botomagien of Coquand), and holds 

 exactly the same position in South India, where it occurs in the lowest beds of 

 our series with Amm. Motomagensis, rostratus, and many other characteristic species. 



^ Species marked with an asterisk (^) also occur in the South Indian cretaceous deposits. 



t Very closely allied to haliotoidea, Sow. 



X Gabb (Pal. Calif., II, p. 275,) identifies this species with Bxogyra carinata ( =:^ plicata, Lam. =^flahellata, 

 Goldf.). 



§ I do not think this change of name will be necessary, because the species belongs to a genus different from that to 

 which it was referred by Coquand. 



