504 PLIOCENE MOLLUSCA. 



The fauna of the Wexford gravels is much newer, having on the whole a 

 northern and Pleistocene rather than a Pliocene character, including abundant 

 specimens of Nassa incrassata, N. reticulata (the most characteristic Red Crag 

 Nassas being altogether wanting), a thick and coarsely sculptured form of 

 Purpura lapillus, with very many species of northern Troplion, Baccinum umhitum, 

 Ocinehra eriiiacea, Scala similis, and many examples of a sinistral Neptanea (not 

 the southern N. contraria of the Crag, but a short tumid form allied to an arctic 

 species, N. deformis — see PI. XXXVI, figs. 30, 31) and other recent shells. The 

 Wexford beds have been described by Mr. Alfred Bell in papers often quoted in 

 this work. The Manxland drift contains a fauna allied to that of Wexford, both 

 of them containing many northern and recent forms with a few of a decidedly 

 Pliocene type.^ An explanation of this well-known mixed character of the Manx 

 shells, so different, as Prof. Kendall observes, from the natural grouping, is that 

 we have in Manxland the remains of two distinct deposits, one older than the 

 other, but this view is not accepted by Mr. Alfred Bell. 



THE PLEISTOCENE AND HOLOCENE DEPOSITS. 



No general agreement has been at present arrived at from the point of view of 

 their marine conchology as to the relation which the various exposures of these 

 beds bear to each other. The fauna of the interesting deposit at Selsey in Sussex, 

 however, deserves a ^^assing notice. Originally described systematically by Godwin- 

 Austen in the Quarterly Journal of the Geological Society for 1857 (vol. xii, p. 4), 

 it has been subsequently studied by Mr. A. Bell, who has collected and identified 

 from it more than 220 species of marine mollusca besides 120 vertebrate and 

 invertebrate forms belonging to other grou^^s. The molkiscan fossils are in 

 unusually perfect condition, many of them being here figured as British for the 

 first time. Taken as a whole they seem to be unique, of a Avell-marked southern 

 character, having no equivalent in any of our post-Pliocene deposits. As to this, 

 reference is suggested to the lists in the undermentioned paper by Mr. Bell." The 

 subject deserves further investigation, though unfortunately it is only occasionally 

 that the Selsey deposit is accessible to the collector. 



The subject of the Crag deposits has been more fully treated by the author in 

 the following papers : 

 1896. " The Pliocene Deposits of Holland and their Relation to the English and 



Belgian Crags," Quart. Journ. Geol. Soc, vol. Hi, pp. 748 — 782. 

 1898. "The Lenham Beds and the Coralline Crag," Quart. Journ. Geol. Soc, 



vol. liv, pp. 808—356. 



1 See Vol. I, p. 123, of the present work. 

 » Rep. Turks. Phil. Soc, 1892, p. 62. 



