Miscellaneous. 247 



first rank Holaster Dewalquei of the Landenian system. This is the 

 first time that the genus Holaster, so abundantly represented in the 

 different stages of the Cretaceous formation, has been met with in 

 the Tertiary. This species, although the last of the series, presents 

 perfectly all the characters of the type ; it is remarkable for its 

 large size, its regularly cordiform aspect, its inflated and subgibbous 

 upper surface, and its angular and very deep anterior groove. M. 

 Manzoni has already noticed in the Tertiary of the environs of 

 Bologna a species nearly allied to Holaster Dewalquei, but distinct, 

 namely Hemipneustes italicus. We may also cite Oaratomus Lehoni 

 from the Laekenian of St. Gilles, a very curious species, differing 

 from the true Caratomi by the structure of the anterior ambulacral 

 areas and the form of the peristome. And we may mention Echinus 

 Colbeaui, which we only know in the state of an interior cast, but 

 which is distinguished from its congeners by its large size, its sub- 

 conical form, its lower surface pulvinate and rounded at the mar- 

 gins, and by its peristome opening in a well-marked depression of 

 the lower surface. Nor must we forget Spatanr/us pes equuli, 

 peculiar to the Eocene of Belgium, and which will always be recog- 

 nized with facility by its elevated hemispherical form, its flat lower 

 surface with trenchant edges, and its very deep anterior groove with 

 keeled margins. — Comptes Rendus, July 19, 1880, p. 182. 



On the Antiquity of certain Subordinate Types of Freshwater and 

 Land Mollusca. By C. A. White, Palaeontologist to the U.S. 

 National Museum. 



Among existing freshwater and land Mollusca there are certain 

 comprehensive genera which may be divided into a greater or less 

 number of more or less distinctly definable groups that are respec- 

 tively recognizable by certain common characteristics, less conspi- 

 cuous than those which separate the larger genera from each other. 

 These minor groups have been treated as genera, subgenera, or as 

 still less important sections by the various authors who have dis- 

 cussed them, according to the individual estimate that has been placed 

 upon the relative value of the characters by which they are recog- 

 nized. It is my present purpose, not to discuss the value of these 

 distinctions as means of zoological classification, but to show that a 

 considerable number, not only of the larger genera of living North- 

 American freshwater and land Mollusca, but also a large propor- 

 tion of the minor or subordinate types which those genera respec- 

 tively embrace, had their origin as such at least as early as the 

 closing epochs of the Cretaceous or the immediately following epochs 

 of the Eocene Tertiary period. 



The fossd collections upon which these observations are based, 

 and which alone are referred to in the following remarks, are those 

 which have been obtained by the different U.S. Government Surveys 

 in the western portion of our national domain. The strata which 

 have furnished these fossils are, in the ascending order, those of the 

 Fox Hills, Laramie, Wahsatch, Green Biver, and Bridger groups. 

 The first-named of these groups is unquestionably Cretaceous ; and 



