OP SOUTHERN INDIA. 271 



centric sulcation, becoming obsolete posteriorly, hinge edentulous ; type, S. atten- 

 uata, M'Ooy, from carboniferous rocks. The peculiar ornamentation is almost 

 the only character by which the species referred to this genus can be distinguished 

 from some species of Leptodomus and Fyrenomceus; it seems rather doubtful 

 that there really exists a generic distinction between all these forms. 



8. Dolahra, M^Coy, 1844, (Garb. foss. of Ireland, p. 64, and Brit. Palgeoz. 

 rocks and foss., p. 269). Shell ovate or trapezoid, gibbose, with a more or less 

 straight hinge-margin, inequilateral, inequivalve, the left yalye being larger than 

 the right, hinge posteriorly with an elongated tooth, sometimes bifid in the left 

 valve; tjipe, I), corrugata, M^Coy. Whether those species which have a crenu- 

 lated or toothed hinge-margin belong to the above genus, or not, remains doubtful ; 

 there seems to be here a similar mixture of species as in Orthonota, 



9. Grammijsia, Verneuil, 1847, (Bull. Soc. Geol., France, iv, p. 696 ; M^Coy, -^^^^^^ 

 Brit. Palseoz. rocks and foss., p. 280; Sandberger, Bhein. Schichtensyst., p. 264). . ' '. :' 

 Shell elongated, sub-equilateral, with prominent and incurved beaks and an exca- 

 vated lunule in front of them, one or two sulci extend from the beaks to the middle 



of the inferior margin ; hinge-line straight, much thickened, without teeth, ligament 

 situated in a groove behind the beaks, muscular scars two, anterior nearly round, pos- 

 terior emarginated above, pallial line entire, but truncate posteriorly ; type, G. pes- 

 anseris, Zeil. and Wirtgen, from the palaeozoic rocks of the Ehenish provinces. 



In external form some species of Grammysia greatly recall Tridacna, but 

 others are closely allied to SanguinoUtes and Leptodomus, 



10. Solemya, Lam., 1818. Shell elongated, oblong, thin, moderately com- 

 pressed, inequilateral, the posterior side being much shorter than the anterior, 

 thin, covered with a shining epidermis, which extends beyond the margins ; hinge 

 with one elongated cardinal tooth in each valve, and a posterior internal rib, to 

 which a portion of the ligament is attached, spreading out near the beak, while the 

 larger portion remains external ; pallial line entire, marginal ; type, S. mistralis, 

 Lam. There are only a few recent species known. One species (new ?) occurs at 

 the Nicobars and in the Bay of Bengal. Possil species are known from all forma- 

 tions down to the Silurian ; at least there seem to be no valid external characters by 

 which the fossil forms could be distinguished from the recent ones. King (Perm, 

 foss. of England, p. 177,) called some Permian species Janeia, but upon a close 

 comparison of these with the recent type species he again cancelled the name 

 (vide ibidem, p. 246). Verneuil's Solemya Uarmica appears to have been taken as 

 the type of Janeia, I have no typical specimens to compare, but if the figure 4, 

 pi. xix, in Geol. of Russia belongs to the same species, and if that figure of the 

 cast is correct, it would appear to be without the elongated cardinal tooth, and 

 consequently distinct from Solemya, but it may be identical with Orthonota. 



The only two cretaceous species of Solemya are from North America, S. sub- 

 plicata, M. and H., Proc. Acad. N. Sc, Phil., viii, p. 288, and S, ventricosa, 

 Conrad, (Smith. Misc. Coll., No. 200, p. 5) ; the last is from Conrad's so called 

 lower eocene beds. 



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