OP SOUTHEEN INDIA. 187 



while the cuspidation recalls the equivalent tooth of Meiocardia. It may also 

 be worthy of notice that the posterior lateral tooth of the left is in all the allied 

 forms of Qlossus always much smaller and more marginal than that of the right 

 valve. 



8. Meiocardia, H. and A. Adams, 1856. Shell trapezoid, inflated, with 

 the beaks distant, strongly in-and re- curved, a ligamental groove extending from 

 each of them posteriorly in a flexuous line ; hinge with the teeth thin, lamellar, and 

 arranged in a line parallel to the superior margin of the shell ; right valve with one 

 angularly bent anterior cardinal tooth, its posterior arm being ascending and very 

 prominent ; posterior cardinal tooth very long, obliquely and obsoletely cross-grooved ; 

 left valve again with an anterior angular cardinal tooth, its hinder portion being 

 higher and longer than the front part which is bituberculated ; posterior cardinal 

 tooth double, being furrowed in its entire length for the reception of the single 

 tooth of the other valve ; posterior lateral teeth distinct, single in the left, double 

 in the right valve. 



The type of this, which I think to be a good genus, is Meiocardia MoUMana, 

 Spengler. The general character of the shell, its thin structure, and the arrange- 

 ment of the hinge-teeth are quite distinct from those of Glossus, in which the 

 posterior cardinal teeth partially overlap the anterior, which become inferior, 

 while such is not at all the case in Meiocardia, in which also the posterior cardinal 

 of the left valve is very different from the corresponding tooth of Glossies. Eomer 

 in his recent Monograph (Mart, and Chem. Conchyl.-kabinet, 1869, vol. x, pt. iii, 

 p. 8, &c.,) only acknowledges two recent species, M, Moltkiana and vulgaris, consi- 

 dering Jf. tetragona, Lamarchii, and Cumingii merely as varieties of the two. 

 Although the form of Meiocardia is very commonly to be met with among fossil 

 shells, I am not acquainted with a single species which, according to its hinge, could 

 be referred to it. It is also impossible to hit upon the authority from whom Chenu 

 (Man,, ii, p. 114), derived his two cretaceous Meiocardice ; the one refers to Isoc. 

 pyrenaica, d'Orb., but where d'Orbigny figured an Isoc. Giierangeri I have not 

 been able to ascertain. The hinge-teeth of the recent Meiocardice are extremely 

 tender and fragile, and the greatest care would be required to expose them properly 

 in fossil forms. 



9. Cardiodonta,^ StoL, 1867, (Laube in Denksch. Acad., "Wien, vol. xxvii, 

 pt. ii, p. 39). Shell cordiform, inflated, with prominent incurved beaks; hinge 

 with two cardinal and one thin or lamellar posterior lateral tooth in each valve ; 

 ligamental groove long, narrow, marginal ; right valve with a strong, grooved 

 posterior and one oblique simple anterior cardinal tooth, the latter running from 

 the beak more or less parallel to the lunular margin ; left valve with a single 

 posterior and a thick anterior cardinal tooth strongly prominent above. 



* The MSS- on the Gastropoda and mostly also on the Pelecypoda of the Balin beds were prepared by me in 1861 

 before my departure to India, and it was I who urged a revision of the work, when in I860 and 1866 my friend, the 

 late lamented Dr. M. Homes, asked me to consent to the publication of my MSS. This fact should have been stated, 

 for in records, published elsewhere, it would appear as if that revision had been done without my having seen the 

 necessity for it. 



