MOLLUSCA OF INDIA. 143 
amined the animal of D. levicula; it is also, I find, a true Macro- 
chlamys. In my paper above mentioned I describe this shell from 
the typical locality (p. 293) in detail, together with another species, 
D. assamica, and two plates (xx. and xxi.) are given; these de- 
scriptions will be given in a subsequent part. 
The Additional and Principal Characters of the Genus Durgella. 
1. The right and left dorsal lobes moderate, the shell-lobes very 
ample; the right shell-lobe extends from the anal aperture (close 
to the upper angle of the shell-aperture) to the columellar margin, 
and spreads away over the shell in a broad triangular tongue ; the 
left shell-lobe is reflected slightly over the edge of the shell in front, 
from near the respiratory orifice, and becomes wider on the lower 
margin as it approaches the umbilicus, and is also of triangular 
shape when extended. A large portion of the shell is always ex- 
posed. 
2. The mucous pore is well developed, with a large overhanging 
lobe. 
3. The jaw is very thin, membranaceous, almost straight on the 
cutting-edge, and with a very slight central projection. 
4, The odontophore is broader than long, with a central minute 
generally bicuspid tooth; the lateral teeth all similar, minutely 
sexcuspid or pectiniform, on a curved edge ; very closely set together 
and exceedingly numerous. +170 .1 . 170+. 
5. In the generative organs an amatorial organ is present in 
some species, absent in others. 
6. Shell thin or membranaceous, globose or depressedly conoid ; 
polished, very closely perforate, the columellar margin haying no 
solidity. 
The abnormality of this genus, as compared with shells of similar 
form, lies principally in the very remarkable odontophore, which is 
quite unlike any other Indian species of the Zonitide that I have 
examined ; with this, of course, we find the jaw also much modified. 
There is considerable similarity with the teeth of Sttala attegia and 
S. infula (figured by Stoliczka in the J. A. 8. B. 1871, pl. xviii. 
figs. 4-9) (vide Plate VIII. figs. 1 e, 2, Part II.) in the multicuspid 
or pectiniform laterals and the greater number (155 on each side) 
in S. infula; but the centre tooth is large, and the shell-lobes of 
the mantle are not developed; still here we have a relationship or 
connection indicated, and shown also in Sitala »hulongensis, G.-A., 
Part II. p. 34 (Plate X. fig. 4), for since describing it I have suc- 
ceeded in finding the lingual ribbon and jaw. There is a minute 
central, with a great number of similar lateral teeth, multicuspid, 
curved outwards, and set extremely close, gradually becoming 
smaller to the outside, and thus similar to those of Durgella levicula. 
This form of odontophore, which I have now observed in several 
species, a list of which I give further on, differs remarkably in type 
of the teeth and formula from other genera of the Zonitide; and I 
consider them a distinct group, having a remote relationship. 
PART ly. 0 
