INVERTEBRATE PALEONTOLOGY. 151 



more conical, and more curved. 1 do not wish to conceal the fact, however, 

 thai the hinge of Veniella is found to vary more or less in these details of the 

 teeth; another well-marked species from the Cretaceous of New Jersey, 

 before me, having the anterior tooth of the right valve distinctly flattened, or 

 compressed, and placed with its longer diameter parallel to the anterior 

 margin of the valve, like that of the left valve in Cyprina. The middle tooth 

 of the left valve is also not always so broad and triangular as in Morton's 

 type-species, as is evident from Dr. Stoliczka's figures of his Indian species. 



When we turn from the hinge, however, to the ense?nble of other char- 

 acters distinguishing these types, it becomes at once more obvious that they 

 present strongly-marked differences. The very gibbous form, prominent, 

 very oblique, strongly incurved, nearly terminal beaks, angular umbonal 

 slopes, strongly costate surface, and generally deep and well-defined lunjule 

 and escutcheon, of the typical group of Veniella, are all in striking contrast 

 with the true cyprinas. Again, in the latter, the anterior adductor muscular 

 impression is directly connected with the pedal scar; while in Veniella 

 proper, as well as in the subgenus Venificardia, so far as I have been able to 

 see, these scars are decidedly distinct. 



I am led to give more weight to these differences, from the fact that 

 they were as strongly marked, even as far back as the Cretaceous epoch, as 

 at any time since. At least, we find our Cyprina ovata, from the Cretaceous, 

 agreeing exactly in every respect with Cyprina proper, not only in all its 

 hinge-characters, but in form, surface-markings, merely evenly convex valves, 

 less prominent, more nearly central beaks, and even in having its pedal scars 

 connected with the anterior adductors. Nor can it be argued that the 

 Venilicardia group (which seems to include some Cretaceous species present- 

 ing very nearly the general form and other external characters, of Cyprina) 

 forms an unbroken transition from Veniella to Cyprina; because the hinge of 

 Venilicardia, so far as yet known, differs much more widely from that of 

 Cyprina than that of Veniella docs. 



I should state here that, although adopting provisionally the name 

 Veniella instead of Venilia, I am not altogether sure that this will be neces- 

 sary. The change was made by Dr. Stoliczka, because Duponchel had used 

 Venilia for a genus of Lepidoptera in 1829. It can hardly be considered a 

 settled question, however, among naturalists, that a change is necessary in 

 such cases, where the genera belong to different classes or subkingdoms ; 



