Terrestrial Operculate Mollusca from Trinidad. — 245 
are the two tentacles with the eyes .close behind them. The 
foot is produced in front into two acute lobes. 
- It may seem strange that so much variation should exist in a 
single species—from a shell with smooth whorls to one with 
whorls bearing a keel ornamented with aculeate projections ; but 
there does not exist in my mind the smallest doubt of the dif- 
ferent forms belonging to the same species. All the forms are 
found existing together in the streams of northern Trinidad. 
Valvata agglutinans, n. sp. 
Shell trochiform-depressed, perforate, entirely composed of nu- 
merous minute grains of mineral matter; whorls 3—4, almost 
carinate, flattened beneath ; umbilicus circular; aperture very 
oblique, circular, the margins shortly-united on the penulti- 
mate whorl; peristome simple, irregular. Height 0-1 inch, 
_ greatest breadth 0°17 inch. 
This very curious little Valvata makes its shell almost entirely 
of minute particles of quartz and mica, the cementing material 
being very limited in amount. It lives on the surface of rocks 
and stones in the hill-streams of the northern part of Trinidad. 
§ 2. Terrestrial Species. 
Cyclotus trinitensis, n. sp. 
Shell depressed, turbinate, rather ‘thick, white under a pale- 
brown epidermis, with fine wavy lines of growth, and some- 
- times with obsolete white or chestnut bands; spire somewhat 
acuminate ; whorls 5, convex; umbilicus broad and open; 
aperture slightly oblique, nearly circular ; peristome blunt, 
its margims forming an angle above; right margin slightly 
sinuate. Operculum concave, with six obliquely striate 
whorls, the inner margins of which are raised. Height 0°55 
. Inch, greatest breadth 0-9 inch. 
~ The animal is of a pinkish colour, which is most pronounced 
about the tentacles. The eyes are small and black. The mouth 
is provided with an amber-coloured, somewhat triangular man- 
dible, divided into two parts by a median fissure, from which 
diverge slightly curved rows of minute denticulations strongly 
resembling the lingual teeth of some Helicidz. 
The lingual teeth are 3.1.3, in arched rows: central broad, 
tridentate; 1st lateral broad, bidentate, with a base much pro- 
duced outwardly; 2nd tridentate; 3rd much hooked and re- 
flexed, tridentate. This dentition is very like that of Cyclophorus 
Tuba (Gray, Syst. Dist. Moll. p. 78). 
- This species is readily distinguished from C. jamaicensis by 
its light colour and by the absence of any ridge round the um-. 
