210 
THE GEOLOGIST. 
columella. In one genus, liowever, Chilina (Gray), the conditions 
of the spire and the apertui-e ai'e much modified ; the columella is 
curved, but is without the oblique twist of the tnie lAmnoea, which is 
replaced by one or more transverse folds. One species in this group, 
C. Pchiielcha (D'Orb.), closely resembles the fossil in question, in the 
relative proportions of the spire and the aperture, and the general form 
and aspect of the shell. In another species, G. Puelcha (D'Orb.), 
the transverse fold is almost obsolete in the young state, and is much 
reduced in importance in the mature shell, while the cui've of the 
columella and the rounded front of the shell correspond with those 
of the Peckham fossil. The Chiliim are described by D'Orbigny as 
inhabitants of the clear running streams and rivers of Chili and 
Patagonia, habitats to which the occuiTence of Glandina costellata 
and of Helix lahjrmtliica as Eocene fossils, would prepare us, in some 
measure, to look tor a living analogue of the form in question. 
Externally the columella of the fossil shells appears to be straight 
and simple, but in specimens, in which the inner sm'face is more dis- 
played, there are indications of a slight and very oblique twist ; and 
I am induced, therefore, on the whole, to consider these shells as 
constituting an aberrant form among the lAmnceidce, partaking of 
the characters of the tiTie Limnma and of Chilina, and to place them 
between those genera under the generic name Fitliarella ; and I dedicate 
the species to Mr. Rickman, by whom attention was first drawn to 
these interesting shells. I subjoin a description of the principal cha- 
racters which distinguish the genus, and also a description of the 
species. 
Kamjpstead, 6th May, 1860. 
Fitliarella (Gen. char.). — Shell sub-cylindrical; spu-e obtuse, more 
or less pi'oduced ; apertm-e oval-oblong, rounded in front, nari'owed 
behind ; columella straight, or very obliquely twisted, arched ante- 
riorly ; outer lip simple, acute ; inner lip thickened. 
P. Rickmani (Spec, descr.) . — Shell oval-oblong, smooth ; spire sub- 
conical, short, varying in height in different specimens ; whorls five 
or six, depressed on the posterior margins, and obtusely angulated 
on the shoulders. The sutural edge is slightly thickened, fonning 
