OP SOUTHERN INDIA. 281 



Mytilicardi(B there should be a small gape; the posterior cardinal is also less 

 elongated in the fossil forms. 



28. JPleuromeris, Con., 1867, (Amer. Journ. Conch., iii, p. 12). Shell sub- 

 triangular, radiately ribbed, hinge in the right valve with one broad, furrowed, 

 recurved tooth, in the left with three teeth, the anterior one small and fitting into a 

 cavity in the opposite valve. Type, Gardita tridentata, Conrad, (Mioc. foss., p. 76). 

 .29. Miodon, Carp., 1864, (Ann. and Mag. Nat. Hist., 3rd ser., vol. xiv, p. 424). 

 Carpenter describes as the type of this genus Jf. prolongatus, a recent species. This 

 shell is ovately sub-trigonal, small, solid, ventrally much produced, with the umbones 

 situated anteriorly, radiately ribbed, the ribs being partially intersected by concen- 

 tric sulcations ; hinge in the right valve with one posterior cardinal and one ante- 

 rior lateral tooth, left valve with one triangular anterior and one elongated posterior 

 cardinal, and a very small anterior lateral tooth. 



It is rather difficult to point out the difference of this genus from Fleuromeris ; 

 both appear to be very much alike, for the interpretation of the hinge-teeth in 

 these minute shells is generally not an easy task. Carpenter says that a species of 

 Miodon made its first appearance in the great oolite with Astarte orbicularis, Sow., 

 (Min. Conch., pi. 444, figs. 2 and 3). Sowerby (1. cit., p. 64,) describes two species, 

 A. orbicularis andpumila ; the figures on the plate have been transposed, neither of the 

 species is radiately ribbed, the first has an anterior lateral tooth in the right valve, 

 the second has an anterior and posterior in the same ; they do not belong to the 

 same genus, but as I am not acquainted with the species themselves, I would not 

 venture to pronounce anything certain regarding their generic determination. The 

 first species is perhaps an Eriphyla (Bosmimm) , and the second a Oouldia, 

 Carpenter further refers to his Miodon an Astarte corbis, which is said to appear 

 among "Searles Wood's Crag series." I do not find the species mentioned in 

 S. Wood's Crag fossils, but he has a Cardita corbis, the description of which closely 

 resembles that of Miodon. 



30. Fteromeris, Con., 1865, (Am. Journ. Conch., i, p. 9). This was proposed 

 for another small triangular radiately ribbed species, Astarte minutissima, Lea, 

 (Cont., p. 64, pi. 2, fig. 39) ; it appears to have two minute cardinal teeth in the left, 

 one in the right valve, and a long posterior lateral in each. In his list of North 

 American eocene shells, (Smith. Misc. Coll., No. 200, 1866), Conrad quotes the 

 same species as Micromeris, which again shows the uncertainty prevailing in the 

 determination of these little shells. Meek in the list of North American miocene 

 shells (Smith. Misc. Coll., No. 183, 1864,) quotes two species, Venericardia 

 fFteromerisJ abbreviata, Con., and V, fFt.J radians. 



31. Cyclocardia, Con., 1867, (Am. Journ. Conch., iii, 191). " Rounded, radi- 

 ately costate, covered with a rough epidermis ; hinge with two robust teeth in the 

 left valve, directed obliquely backwards, the posterior one elongated and slightly 

 curved; anterior tooth of the right valve rudimentary." Type, C. borealis, Con- 

 The author states that this form differs from Cardita by the rough brown epidermis' 

 and by the anterior cardinal tooth being obliquely directed backwards, and an 



