OF SOUTIIEEN INDIA. ^ 155 



d. Sub-familj/,—BOSINIINJS. 



The animal of Dosinia has prolonged united siphons, sometimes, in other genera, 

 scarcely separated at the end, and occasionally with fringed orifices ; foot large, 

 sub-quadrangular, anteriorly slightly produced ; mantle plicated at the edge ; the 

 inner lamella of the gill larger than the outer one. 



Shell more or less suh-orbicular, solid, sometimes slightly elongated and 

 inflated, of a thin structm'e ; surface concentrically striated or laminated, pallial 

 sinus triangular, pointed at the end, ascending. 



If the animals were in all the forms now referred to this sub-family so cliar- 

 acteristically different by their united siphons and the form of the foot as is, for 

 instance, D. liqjiiia from the animal of Cytherea and Tapes, there certainly would exist 

 strong reason for the classification in a distinct sub-family, if not a separate 

 family. As regards the form of the shell the group is not difficultly defined. Fossil 

 evidence goes also to show that at least a special sub-family should be established, for 

 numerous, some different, but, on the whole, characteristic types are already iu the 

 cretaceous period to be met with, and possibly they may also be found in lower 

 strata ; the general shape of the shell is not wanting in them, but the hinge-teeth 

 have not yet been examined. I especially mean here to refer to the various forms 

 of Astarte and Lucina-\i\s.G shells iu the Oolites. 



There is also another somewhat different type of shells classed in this 

 sub-family, one represented by the recent dementia, and very likely indicated 

 already in the cretaceous period. These shells are less distinctly orbicular, 

 but more elongated, inflated, remarkably thin, and concentrically sulcated. I 

 liave not had as yet the opportunity of observing the animal of dementia, but I 

 greatly suspect that this is not its proper place in the system. I would be 

 much more inclined to regard these forms as belonging to the Gzauconomtid^, 

 as already stated (p. 91). The shells are really, except in a few points of 

 detail, as different in their whole character from those of Dosinia as they could 

 be. Still as long as direct proof is not obtainable, it would be to no advantage 

 to place them anywhere else. It is to be expected that sooner or later some 

 thorough reform must be made in this sub-family. I have already alluded to 

 the difficulty of classifying satisfactorily such forms as Liicinopsis ( Mijsia of 

 Gray), and the same is here partially the case with Cyclina. The shells of botli 

 have a very great resemblance, but the animal of the former has, though short, 

 still quite separated siphons ; of the latter Gray says, "Animal Dosinice simile." 



12. Dosinia, Scopoli, 1777. Shell orbicular, or trigonally sub-orbicular, solid, 

 moderately convex at the sides, with pointed and slightly incurved beaks, concen- 

 trically striated or sulcated ; lunula always circumscribed, often deeply excavated ; 

 sinus triangular, pointed ; ligament usually in a deep groove ; hinge with three car- 

 dinal compressed teeth in each valve, one anterior small lateral in the left valve 

 fitting into a corresponding cavity of the right ; this lateral tooth is sometimes 

 nearly obsolete. Thus, as regards the dentition of the hinge, Dosinia may be con- 

 sidered intermediate between Venus and Cytherea, but distinctly inclining to the 

 latter, especially to the sub-genus Caryatis, as indicated by species like D. trixjona, 



