the Cyclostomacea of Eastern Asia. 455 
Of these, L. Cybeus I consider a Cyclophorus, probably only 
adolescent ; and my impression, derived from a comparison of 
the type-specimens in Mr. Theobald’s cabinet, and of some fine 
and fresh examples of C. zebrinus, Bens., from the same locality, 
was that the former were merely a variety, perhaps immature, of 
the latter. 1 would, however, wish to repeat the observation 
before expressing a definite opinion, and merely suggest the idea 
as probable. 
L. Burmanum, Pfr., I have not seen; but it also appears, 
from the description, to be very probably an immature Cyclo- 
phorus, many young shells of that genus having very thin and 
membranaceous opercula. In this, as in so many other cases, 
the characters of the operculum alone are insufficient for generic 
distinction. 
The sole remaining species, L. aspirans, Bens., is a true Lepto- 
poma, with the peculiar form, peristome, and texture of shell 
characteristic of the genus. It has a wide range, being found 
in the Tenasserim provinces, near Bassein in Pegu, and through- 
out Arakan as far north as Akyab. 
It is only by confining the name Leptopoma to the peculiar 
and well-marked type, species of which are so numerous in the 
Indian Archipelago and the Philippine Islands, that it can be 
considered to have claims even to subgeneric distinction. At 
_ the best it appears to have no better claim to be separated from 
Cyclophorus than has Myaostoma or Lagocheilus ; and its proper 
position is probably as a subgenus. 
15, Atycaus, Gray. 
This genus was founded on a solitary species from Cochin 
China, and only three forms were enumerated in Dr. Pfeiffer’s 
monograph published in 1852. In 1858 the number had in- 
creased to fourteen, almost all the additional species being from 
the Indian area. I now possess no less than thirty-five species, 
being all the described Indian forms with the exception of A. 
Andamanie, Bens., and all others, so far as I am aware, except 
A, gibbus, Fér., and A. pilula, Gould. 
The known forms from the Indian and Burmese area amount 
to thirty-one, of which one has not yet been described. No 
type in the whole order is better characterized nor more distinct 
from all others, no approach to a passage into any other genus 
being yet known. I have already referred to the broad distine- 
tion between Alyceus and Cyclotus; the former is equally dis- 
tinct from Cyclophorus, despite the similarity of the operculum. 
But the singular and anomalous form of the shell induces me 
to believe that it can best be classed in a subfamily by itself ; 
and this view is borne out by the peculiar texture of the shell, 
