EDWARDS — ON PITHAEELLA EICOIANI. 209 



stone of Rilley-la-Montagne, and other estna^rine forms ; and also 

 masses of leaves of trees, and other vegetable remains. Associated 

 witli these are found, sparingly in the clay, but rather more plenti- 

 fully in the sandstone band, the remains of an nndescribed spiral 

 shell, which were at first referred to the genus Vohita, because the 

 imperfect casts, in which condition only they were then found, pre- 

 sented a close resemblance to casts of the well known Bognor fossil. 

 Valuta denudata. Tolerably perfect specimens have been since ob- 

 tained, and from these it appears that the columella is without 

 the plaits characteristic of that genus, and that the base of the shell 

 is rounded and entire, and without transverse furrows. The shells, 

 therefore, must be referred, not to the genus Volufa, but to some 

 land or fresh-water mollusc, belonging most probably to one of the 

 three families, Auriculidw, Achatinidce, or Limneidw. 



The shells are smooth and rather thick, and in their general aspect 

 present much of the character of the Auricididw, and were there any 

 indication of transverse folds in the columella, they might fairly be 

 considered to be an aberrant form in the group (Aimcula, Lam. 5 

 Geovula, Swains.), of which A. auris-Midce forms the type. The 

 prominent character by which the shells of the Auricuhdse are dis- 

 tinguished is the presence of one or more thick, well-defined, trans- 

 verse folds on the columella, and this is, I believe, a constant 

 character : I do not know of any genus belonging to the family in 

 which it is wanting, or evanescent. 



The AclmtinidcB, as a family, are characterized by the truncation 

 of the columella ; and they usually have the spu-e much produced, so 

 as to exceed the aperture in length. One group in this family — in- 

 habiting the West India islands and the adjacent parts of the 

 American continent, (Folyj^hemus, Montf., Glandina, Schum.), in 

 which the aperture and spire are nearly equal, and to which the 

 Peckham shells approach more closely than to any other genus in the 

 family — is represented in our Eocene fauna by AcJiatina (Glandina) 

 costellata of the upper fresh- water deposits in the Isle of Wight ; but 

 in this group the body whorl is much attenuated at the base, and the 

 columella is strongly truncated. 



The distinguishing characters of the lAmneidoe are the acute spire, 

 the wide aperture rounded in front, and the obliquely twisted 

 vol.. HI. 2 D 



