﻿274 GASTEROPODA OF THE INFERIOR OOLITE. 



Note. — Hitherto it has been possible for the most part to assign a family 

 position to the genera of Gasteropoda occurring in the Inferior Oolite ; but we 

 now are called upon to consider several groups of shells, more or less turbinate 

 in character, whose family position cannot with certainty be defined. The 

 majority of these were referred to Turbo by d'Orbigny. 



The following genera are included in the above category, viz. Amberleya, 

 " Littorina" Cirrus (including Hamus ina), and Straparollus (including Discohelix). 



Preliminary Note on Amherleya and " Littorina. ," 



There is a twofold difficulty attendant on dealing with the numerous species 

 of fossil shells which I propose to place under one or other of the above genera. 

 To the uncertainty of family affinities there is also to be added the difficulty of 

 synonymy. The former is, of course, the more serious difficulty of the two ; for 

 if we are wrong in supposing that Amberleya, Eucyclus, &c, belong to the Littori- 

 nidse, in that case we are not justified in assigning the generic term "Littorina" 

 to the group of smaller species which are associated with them. The older 

 writers, and particularly d'Orbigny, regarded nearly the whole of these forms as 

 belonging to the Turbinidse, and the modern tendency seems to be to revert to 

 that conclusion. We may use Amberleya or Eucyclus without pledging ourselves 

 to the family affinities of the genus, but if we use Littorina or Turbo the case is 

 different. In the following pages " Littorina " is used only in a conventional 

 sense. 



In 1851, Morris and Lycett (' Grt. Ool. Moll.,' p. 54) thus diagnosed 

 Amberleya: — "Shell turrited, turbinate, apex acute; whorls flattened above, 

 convex and nodulated beneath, the last whorl ventricose ; aperture ovate, entire ; 

 inner lip thickened and nearly covering a small umbilicus ; sutures deeply 

 impressed ; no columella." 



The genus Eucyclus was constituted by J. A. Deslongchamps (' Bull. Soc. Lin. 

 Norm.,' vol. v, p. 23 of separate copy) in I860, being based on Turbo ornatus, 

 Sowerby, and similar shells. The author alludes to Aberleya (sic). He 

 considered that genus to have been established on bad specimens, and to have been 

 imperfectly characterised. His own diagnosis of Eucyclus is comprehensive 

 enough. It contains most of the points in the diagnosis which I offer below. 



There can be no doubt that Deslongchamps' diagnosis was far more accurate 

 and full than that of Morris and Lycett, which was little better than a description 

 of one species. At the same time Deslongchamps, when he alluded to Amherleya, 

 seems unconsciously to admit that his new genus might possibly be covered by 

 that of the authors of the ' Great Oolite Mollusca.' 



