the Cyclostomacea of Eastern Asta. 4.43 
position of Diplommatina, of all the Cyclotine, and of the Indian 
forms ascribed to Hydrocena. 
1. TruncaTELLA, Risso. 
Only a single species of this genus (7. Ceylanica, Pfr.) is 
known to inhabit Ceylon, and none have as yet been met with 
elsewhere in India. The species, so far as I am aware, presents 
no peculiarities. 
2. DretomMatina, Bens. 
Dr. Pfeiffer, in his monograph, placed this genus between 
Alyceus and Megalomastoma; in the Supplement, he makes it 
the type of a totally distinct family, of the suborder Opisthoph- 
thalma, which is characterized by the eyes being placed above 
the base of the tentacles. I have never seen living specimens of 
any of the Aciculide; but, judging from the plates in Adams’s 
‘Gen. Rec. Moll.,’ the position of the eyes is very similar to that 
seen in the Auriculacea. This is by no means the case in Di- 
plommatina, in which genus the eyes, although higher in position 
than in other Cyclostomaceous genera, are rather at the side of 
the head than above it; and there is no trace of the long pro- 
boscis of Truncatella. The operculum also is concentric and 
horny ; but, from the minute size of the species, and the manner 
in which the operculum is withdrawn far within the shell, it is, 
in most cases, difficult to examine it. In some species, as in 
D. Nilgirica, W. & H. Blanf., the spiral structure is obsolete. 
The Indian Diplommatine may be divided into two groups, 
with distinct geographical distribution. The more numerous 
type inhabits the Eastern Himalayas and Burma, and comprises 
the following species :— 
D. pachycheilus, Bens. Sikkim. 
D. pullula, Bens. Sikkim. 
D. Blanfordiana, Bens. Sikkim. 
D. diplocheilus, Bens. Khasi Hills. 
D. polypleuris, Bens. Khasi Hills. 
D. exilis, W. Blanf. Ava. 
D. Pappensis, W. Blanf. Ava. 
D. sperata, W. Blanf. Pegu; 
and two other species from Pegu as yet undescribed. These are 
all characterized by a continuous peristome (the upper portion 
being broadly appressed on the penultimate whorl), the presence 
of a columellar tooth, and by strong transverse (vertical) costu- 
lation on the whorls. The antepenultimate whorl is far broader 
than the rest, and the spire above it is more or less acuminate. 
The two species from the peninsula of India described by my 
brother and myself, viz. D. Nilgirica from the Nilgiri Hills, and 
29% 
