OE SOUTHEEN INDIA. 185 



carefully examined, many more genera may be added to this sub-family, showing 

 it to be one of the most important in fossil Conchology. 



2. Apricm^dia, Gueranger, 1867, (Album, paleont. du Dept. d. 1. Sarthe, &c., 

 expli., p. 13, pi. 16, fig. 21). Shell elongated, inequilateral, like a Trapezium, 

 solid; hinge with one strong, recurved tooth in each valve, the tooth being in 

 the left valve almost directly under the beak and in the right a little posterior 

 to it ; to each tooth corresponds an equally large cavity in the other valve. 



This peculiar form resembling Trapezium is distinguished by the simple form of 

 its hinge ; it is based upon a cretaceous species, Apr, carinata, 



3. Anisodonta, Desh., 1860, (Paris foss., 2nd edit., i, p. 542). Shell ovately 

 elongated, compressed, inequilateral; hinge with one sharp tooth in each valve 

 and a pit beside it, fulcra distinct, short, thick. Such is the distinctive character- 

 istic given by Deshayes of a small fossil shell, A. co7nplanatum, from the Paris 

 basin ('' sables marins inferieurs de ChMons-sur-Vesle"). It is not perfectly plain 

 what is meant by the pit next to each tooth. The figure shows in the right valve 

 a large broadly triangular and in the middle apparently excavated tooth just below 

 the beak, and in the left there is one stronger anterior compressed tooth and one 

 smaller posterior in front of the fulcrum ; probably this is more correct than the 

 description ; the muscular impressions are elongated and pallial line entire. The 

 general form of the shell is that of typical Trapezia, 



Faujas-Saint-Pond published in 1808 (Annales du Museum, Paris, xi, 

 p. 384, &c.,) a short account of a fossil shell from the tertiary deposits of Italy, 

 naming it Clotho (non idem, Walckenaer, 1807, ArachnoideaJ. This shell resembles 

 in form Anisodonta, except that it is a little less inequilateral and apparently of 

 very solid structure, but the hinge-teeth are remarkably similar to those noticed 

 in the last genus. The author says that there is one bifid tooth in each valve, 

 somewhat compressed and recurved towards the beaks, one tooth being much larger 

 than the other ; two muscular impressions and an interior ligament. The accom- 

 panying figure shows one large triangular bifid tooth in the right valve and one 

 compressed, descending long tooth posterior to it ; in the left valve there is one 

 large anterior and one small posterior tooth, and an additional short compressed 

 descending tooth behind the beak. The difiiculty is how to explain in Paujas- 

 Saint-Pond's figures the posterior descending teeth; if these are equivalent to 

 what Deshayes considers to be the fulcra in Anisodonta, in which they are, 

 however, ascending, we have a perfect analogy between the two shells in question, 

 and they may still be referable to the same genus. I do not think this to be at all 

 improbable, for the arrangement of the Jiinge-teeth in both, Anisodonta and the 

 form called Clotho, are in principle very much the same as those of Trapezium, 

 with a species of which Clotho has apparently been found. However, if the 

 posterior descending teeth of Clotho are to be looked upon as cartilage processes, 

 the shell must be referred to the corbulinm close to Sphenia, In spite of 

 P.-S.- Pond's statement, that the ligament is internal, I do not think the latter case 

 more probable than the former; neither can it be decided by a reference to 



2 Y 



