458 CRETACEOUS PELECYPODA 



Menard), 3Iunsten, Hag., ostracina* Lam., ( = /luliotoidea, Sehloth., = coniu-arietis, Nilss., 

 = siomatoidea, Forbes), jjlici/era, Duj., FiiscAu,f Coq., reticulata, Gein., sigmoidea, Reuss, 

 Sollieri, Coq., squamtda, Reuss, striato-costata, Eichw., Tamidka* Stol., Texana,X Rcem., 

 Trauisclioldi, Coq., ( = contoHa, Eichw. ex parte), Washhujloni, Coq;, (= parasitica, \ Gabb). 



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



1. ExOGYRA HALIOTOIDEA, Sowerbjj, PI. XXXVI, Fig. 7, and PL XXXVII, 



Figs. 1-3. 



1813. Chama haUotoidea, Sow., Min. Conch., i, p. 67, pi. 2a.—Gryph(Ba, Ejcogyva, aut Ostrea eadem 



auctoruin. 

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

 1869. Ostrea, lucifer, Coquand, Monog. Ostr. cret., p. 43. 



Ex. testa late semiovata, mtriforme, dejn^essa, suh-lceclgata, ad marginem dor- 

 salem convexa, ad ventralem rectiuscida ; valva affixa planulata, nommnquam irregu- 

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

 valde intorto, valva libera fere plana, ad marginem convexum aliqiiantum incrassata, 

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

 impressione musmlari mibcentrali, magna, elongate ovata. 



Forbes already noticed the great similarity of his E. orientalis to the 

 European E. haUotoidea, 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 difference 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 Forbes' 

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

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

 also becomes obsolete. 



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

 Formation. — Ootatoor group. 



E. haUotoidea has been found in the Upper Greensand of England, at various 

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

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

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

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



* Species marked with an asterisk {*) also occur in the South Indian cretaceous deposits. 



t Very closely allied to haUotoidea, Sow. 



X Gabb (Pal. Calif., II, p. 275,) identifies this species with Exogyra carinaia ( = plicafa, Lam. ^Jiahellata, 

 Goldf.). 



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

 which it was referred by Coquand. 



