116 Dentition of Pulmonate Mollusks. 
found in Cylindrelia ; no upper median ribs en chevron, but all the ribs slightly 
oblique. 
Lingual membrane (PI. XJ, fig. F); centrals tricuspid, laterals bicuspid, 
each cusp with long cutting point. 
(c) JAW WITH SEPARATE, DELICATE RIBS, USUALLY RUNNING 
OBLIQUELY TOWARDS THE CENTRE. 
Several species are fuund in the last genus with this type of 
jaw. 
Gzotlis. 
The genus Ga@otis was described by Shuttleworth,* founded 
on a curious mollusk from Porto Rico. The lingual dentition 
was said by him to be nearly the same asin Vitrina and Zonites, 
the teeth arranged in oblique rows, centrals obtusely tridentate, 
laterals scarcely differmg from the centrals, marginals length- 
ened, awl-shaped, arcuate, at base ? bifurcate. The presence of 
a jaw was not verified by Shuttleworth. The character of the 
dentition was considered such as to denote carnivorous habits of 
the animal. 
An examination of an unidentified Porto Rico specimen (Mr. 
R. Swift) has furnished the following description. 
Gaotis 
Jaw (Pl. XV, fig. A) long, low, slightly arcuate, ends attenuated, ex- 
tremely thin and delicate, transparent; in one single piece, but divided by 
over forty} delicate ribs into as many plate-like compartments of the type 
common in Cylindrella and Bulinilus, but with no upper median triangular 
space; the ends of the ribs serrate the upper and lower margins. 
Lingual membrane (Pl. XI, figs. H, I) long and broad, composed of nu- 
merous rows of teeth arranged en chevron. Centrals with base of attachment 
very long, narrow, obtuse above, incurved at sides, obtusely rounded and 
expanded at base, near which is a short, gouge-shaped, expanded cusp, 
whose lower edge has three bluntly-rounded cutting points. Laterals same 
as centrals in shape, but a little larger, and asymmetrical from the dis- 
proportionate expansion of the cutting point. Marginals same as laterals, 
but more slender, with more developed and graceful cutting points, of 
—— 
* Feérussac’s figure of Parmacella palliolum seems to show a jaw with stout 
ribs; I do not think Gaolis can belong to the same genus, Peliella. 
+ Fragments only of the jaw were saved; the largest one I have 
figured, and from it estimate the whole number of ribs. 
