244 PROCEEDINGS OF THE SCIENTIFIC ASSOCIATION. 
from it by the absence of a parietal plait and by its fine 
ribbing. I found it near Turure on th6 road to Mayaro. 
Autonoe n. gen. 
Terrestrial Inoperculata with ovate obconoidal thin horny 
shells having a compressed body- whorl slightly angulate 
above ; a short conoidal spire and a long narrow aperture 
a little dilate anteriorly, the outer margin simple and the 
columella tortuous, bearing a strong plait. 
This genus is probably closely allied to Melampus and 
Laimodonta , differing chiefly from the former in its thin and 
horny shell and from the latter in its short spire and longer 
aperture. 
Autonoe riparia n. sp. 
A nearly smooth ovate obconoidal thin horny shell of 
about 5 whorls, the last somewhat compressed, whitish 
under a straw-colored epidermis ; suture shallow, rather 
irregular ; aperture elongate, widened below, inner margin 
covered with a callus and furnished with a strong plait • 
columella strongly twisted. Length 10 mill., breadth 6. 
In shape this shell resembles Melampus pusillus ; its thin 
texture however scarcely allows of our referring it to Me- 
lampus. If one compares the present species with 'M. pusil- 
lus , it will be remarked that in addition to the very great 
difference of texture, A. riparia has a shorter spire, a per- 
fectly simple outer margin, and is destitute of the posterior 
parietal plait as well as of the internal ridge of the outer 
lip. Unfortunately I secured only one example of the spe- 
cies. I found it on Mayaro Point amongst the bushes some 
ten or twelve feet above the highest limit reached by the 
waves of the sea, a habitat, it will be noticed, very similar 
to that of the Aurieulidee. 
