Fluviatile Mollusca of Trinidad. 51 
Lingual teeth numerous; medians minute, simple ; laterals 
symmetrical, tricuspid, central cusp much the largest. 
I cannot separate this species from S. ¢erebraster, Lam. 
TORNATELLINA, Shuttleworth. 
Tornatellina lamellata, Pot. & Mich. 
Leptinaria antillarum, Shuttleworth. 
This species is viviparous. In July and August it is found 
full of young shells. It is terrestrial, beg found chiefly among 
decaying wood and vegetable matter. 
Lingual teeth numerous; medians small, simple; laterals 
with a single, long, acute, pellucid cusp, and two obsolete denta- 
tions on the outer side. The mandible is somewhat horseshoe- 
shaped, apparently composed of a number of pentagonal prisms 
laid obliquely, resembling the shell-structure of Brachiopoda. 
PLEeKocHEILvs, Guiding. 
Plekocheilus auris-sciuri, 0. sp. 
Shell vimate, oblong-conie, solid, silky-shining, with longitudinal 
lines of growth which become somewhat smoothly squamose 
on the last whorl; wholly white, or more often marbled, 
spotted, or striped longitudinally with fuscous or chestnut 
on a whitish, yellowish, or pinkish ground; whorls 6, rather 
convex, the last one compressed near the aperture; suture 
followed by an impressed line, which is more distinct on the 
last whorl ; aperture constricted, angularly suboval ; peristome 
white, expanded and reflected, much thickened, especially in 
the middle of the outer margin; inner margin sinuate, thick- 
ened and reflected over the umbilical fissure, bearing an obso- 
lete tooth at its termination on the penultimate whorl; margins 
joined by a thin callus extending into the interior, under 
which is usually a stripe of chestnut-colour ; columella with 
a strong fold. Height 1:65 inch, greatest breadth 0-7 inch ; 
height of aperture 0°65 inch. 
This very peculiar type of shell is represented in St. Vincent 
by P. undulatus, a species allied to the present, from which it 
may be distinguished by P. auris-sciurt being generally smaller 
and very considerably narrower in proportion to its height. 
The aperture is more angular and more produced anteriorly. 
P. auris-sciuri is therefore of the two the form that shows the 
greatest divergence from Bulimus. P. distortus, Brug., a Ve- 
nezuelan shell, shows a still greater divergence from the type- 
forms of Bulimus. P. distortus is a longer and larger shell than 
the Trinidad species, and it is much narrower in proportion to 
its length. P. auris-sciuri has its whorls more couvex, and the 
4r* 
