1884.] NATURAL SCIENCES OF PHILADELPHIA, 109 



1864. Saxicava bicrisfata Sandb. 



Speyer, Tertiaerfauiia v. Soellingen, Palaeontogr., ix, p. 48. 



1867. Saxicava arctica L. 



Weinkauff, Conch yl. d. Mifctelmeeres, i, p. 20., 



1868. Saxicava arctica L. 



V. Koenen, Marin. Mitteloligocaen, 2d part, Palseontogr., xvi, p. 266. 



Two specimens of Saxicava hilineata Conr. from the American 

 Miocene prove to be the same variety as S. hicristata Sandb. 



Wood has alread}- said in 1848 (Crag. Moll. p. 288) : ^^ Saxicava 

 bilineata Conr. is probably another variety of this species " 

 (S. arctica). 



I cannot see in tlie fignre of S. Jeurensis Desh. any difference 

 from our species. Y. Koenen seems to be of the same opinion. 



Saxicava arctica L. seems to be generally distributed in the 

 older and later Tertiary and in the present time on both sides of 

 tlie Atlantic. 



New species were found bj^ me in Claiborne snnd, belonging to 

 the American Museum of Natural History in New York, and 

 which had been examined several times before. Afterwards I re- 

 ceived sand from Claiborne myself and found most of these species 

 again, as well as others that are new. Onlj- the three following 

 species, however, are published here, chiefl}^ because the state of 

 the literature on North American Tertiary invertebrates makes 

 it almost impossible to determine with certainty new species and 

 to find and to describe the differences from similar forms, already 

 named.* 



* In White's Bibliography there are given nearly seventy papers of the 

 main author of this literature, T, A. Conrad, containing notes on American 

 Tertiary niollusks ; and even this list is not complete. Conrad's description 

 and figures are mostly poor or very poor. He published a great many 

 fossils without figures, many without localities, and not a few without 

 giving even the formation ; I have also found one without a name (Proc. 

 Ac. Phil., 1862, p. 288). In his two check lists of the older Tertiary 

 (1865 and 1866) he ignores the species of H. C. Lea, and does not 

 give an account even of all his own. Having a tendency to describe a 

 variety as a new species and a species as a new genus, he found, of course, 

 that not only the Miocene species are all diftercnt from the Eocene ones, 

 but that even the groups of tl^c Am. Eocene "hold few, if any, species in 

 common." 



