OF CONCIIOLOGY. 99 



Circe; fig. 3 as Dosinia, and fig. 4 as Gyclina. He also figures 

 5 species of Venilia, Morton, under tlie heads of Cypricardia, 

 Gyprina, and Isocardm. Girce, Dosinia and Gyclina did not 

 exist before the Miocene Period. In order to form a 

 more natural system from new comparisons of the natural 

 ajQ&nities of families and genera, an extensive revision of 

 fossil groups will have to be undertaken to rescue them 

 from the highly artificial classification which yet obtains, the 

 sanction of authority. Analogy only, however, can be brought 

 to bear on organic remains, but this of itself can enable us 

 to approximate a more natural arrangement than at present 

 exists. I believe that many genera perished with the Creta- 

 ceous fauna, which are yet credited with Tertiary and existing 

 species. For instance, the genus Venericardia is supposed by 

 D'Orbigny to be represented by a few species in the Creta- 

 ceous period; but a glance at his figures is sufficient to show 

 them to be distinct. I believe the genus Venericardia came 

 in, for the first time, with the Eocene fauna, and in vast abund- 

 ance.* 



The genus Meeh'a, Gabb, I accept as a natural group of the 

 family Gyprinidse, and his Meekia sella as distinct from the 

 Oregon Gyprina bisecta (Eocene.) The hinge of the latter I 

 have not seen ; but, as the shell is said to have a palleal line 

 without a sinus, I presume the genus to be either Gyprina^ or 

 one nearly related to it. 



VOLUTID^. 



YoLUTiLiTHES Navarhoensis has the external sculpture 

 and form of a species o^ Eostdlites^onvLd in New Jersey, which 

 I have supposed to be identical with R. Texana. The number 

 of folds may prove it distinct from the Texas species, but I 

 have no specimen for comparison, and I believe the number 

 of columellar folds varies in the same species. 



Fasciolaria elongata, Sowerby, is an European species, 

 very similar in sculpture to tiie American species, as repre- 

 sented in Mr. Gabb's figure of his V. Navarroensis. This 

 genus is limited to the Cretaceous era. 



SYCOTOPYD^. 



Perissolax, Gabb, is limited to the one species, but it is 

 very different from Busycon Blakeyi, Conrad. That species 

 is nearly related to Levifusus traheatus, Conrad, of the Clai- 

 borne (Alabama) locality .f 



*The shells described hy Dr. Zittel, under the names of Cardita Reynesi 

 and G. granigera, are species congeneric with D'Orbiguy's Cretaceous 

 Carditm. 



t Perissolax brevirostris represents another genus. 



