364 AMERICAN JOURNAL 



Conrad. This genus is peculiar to the Eocene formation, and 

 may be distinguished from Pyrula by its elongate form, the 

 canal being longer and narrower than in the allied genus, and 

 by its nodes and ribs. 



Chemnitzia Spillmani, pi. 10. fig. 70, is very distinct from 

 the species I described under that name. The outline of the 

 two species is very different, the Spillmani rapidly decreasing 

 in size from the aperture, and Mr. Gabb's shell very gradually. 

 His shell is smooth on the under surface; the Spillmani is 

 slightly convex on the base, with 5 or 6 impressed revolving 

 lines and the ribs crenulated or subnodose. 



Aturia Matheivsonii is Aluria zic-zac^ or, if it should be dis- 

 tinct, it would be the same as A. anjitstata, Conrad. The ge- 

 nus is peculiar to the Tertiary, and the zic-zac never found 

 above the London Clay or Older Eocene in England and the 

 Paris Basin. It is found in Older Eocene rock at Canada de 

 las Uvas, in company with a Venericardia, very similar to V. 

 planicosta [Cardita Hornii, Gabb.) It is probably identical 

 with the 2)ittm'costa, and seems to belong to the var. regia, of 

 the Older Eocene of Maryland, which varies from planicosta 

 only in the ribs being distinctly separated at base. 



Dosinia elevata, Gabb, pi. 20, fig. 252, is Dosiniopsis ulta, 

 Conrad, which is very near to, if not identical with Dosiniopsis 

 Meekii, Conrad. The specimen I described as D. alta, was so 

 very imperfect, that I should not have suspected its identity 

 with D. Meekii, had it not been better represented in Mr. 

 Gabb's figure. This shell is peculiar to the Older Eocene. 



Dosinia Uvasana, pi. 30, fig. 248, is Dione ovata, (^Cytherea,) 

 Kogers, found in the Older Eocene of Virginia. Gytherea 

 pyga, Conrad, is probably a variety of this species. 



Meekia sella, pi. 25, fig. 179, is probably Cyprina hiseda, 

 Conrad. (Eocene.) 



M. navis, fig. 180, is a species of Yoldia. 



Mactra Ashhurnerii, fig. 127, is probably M.alharia, Conrad, 

 (Eocene.) Two species have been confounded, one Cretaceous, 

 and the other Eocene. One he describes as having "regular, 

 nearly uniform, rounded concentric ribs," and another as hav- 

 ing only fine lines of growth. The former is probably a Cre- 

 taceous species, whilst the latter corresponds with the Eocene 

 alharia. 



Nucula truncata, pi. 26, fig. 184. Two species are evidently 

 confounded under this name. Mr. Gabb should have figured 

 a specimen from each division, as he has done in Amauropsis 

 alveata. 



