190 LAND AND FRESHWATER 
to be formed more rapidly, and finally the thickened double peristome 
is completed. ‘That the mantle-edge has a tendency to expand and 
grow, taking on a wavy outline, is shown in those species with 
deeply crenulated lips. 
We have in the genera Pterocyclos, Spiraculum, Rhaphaulus, 
Alyceus, Diplommatina, and Opisthostoma that indication of continual 
development going on, and assuming great diversity of form aiter a 
certain stage of existence, which has been so often brought to 
notice in other groups of animals, showing that these shells are the 
more modified descendants of older and less specialized forms, that 
reached and brought their shell-constructing powers to an end at an 
earlier stage of growth. Alyceeus with the shell cut back to the 
posterior end of the sutural tube and supplied with a thickened lip 
would be in all respects like many simple forms of Cyclophorus. 
Rthaphaulus would be a Megalomastoma. In Diplommatina the 
change would appear shown at the constriction of the last whorl. 
Alyceus is essentially of a burrowing habit, and I have often 
obtained them quite deep in the moist soil; this is perhaps the 
reason of the eyes being so much smaller in comparison to those of 
Diplommatina. The shells when taken fresh are generally coated 
with a black clayey substance completely concealing the surface and 
its costulation. In favourable localities, among the deep layers of 
black decaying leaves, they are very numerous and easily found. 
ALycz£vs cGemmuLa, Benson. (Plate XLVIII. figs. 4, 4a, 48, 4c.) 
Locality. Rungun Valley, near Darjiling (ex coll. W. 7’. Blanford). 
Alyceus (Charax) gemmula, Benson, A. M. N. H. 1859, vol. iii. 
pp. 177,179; Pfr. Mon. Pneum. vol. iii. p. 52 ; Hanley, Conch. Ind. 
p- 38, pl. xeili. fig. 7; Theob. Supp. Cat. p. 39; Reeve, Conch. Icon. 
1878, pl. v. fig. 37. 
Original description :—* Testa umbilicata, conoideo-depressa, 
levigata, nitida, ad ventriculum minutissime, ad umbilicum crasse 
striata, hyalina ; spira concidea, apice obtusiusculo, sutura profunda ; 
anfractibus 4 convexiusculis, ultimo compresse rotundato, twin tumido, 
tubulum mediocrem gerente, tunc fossiculato-constricto, strictura erista 
recumbente, demumque area planata ab apertura separata ; apertura 
obliqua, superne arcuatim prominente, peristomate duplici, valde in- 
crassato-reflexo, intus superne ad angulum et infra ad basin leviter 
emarginato ; umbilico profundo. Opere. 2 
“ Diam. major 2}, minor 14, axis 13 mill. 
“ Habitat rarissime in valle Rungun. 
‘“‘Of this little shell the sole specimen obtained by Mr. Blanford 
was forwarded to me for examination. Its affinities are with the 
Khasia A. hebes ; but it is perfectly distinct in colour, smaller size, 
sculpture, narrower constriction behind the ridge, narrower umbilicus, 
and in the emargination visible within the aperture at the lower part.” 
ALYCHUS PACHITAENSIS, n. sp. (Plate XLVIII. figs. 5,5, 50, 5c.) 
Locality. Pachita village (Camp no. 7 of the Expeditionary Foree, 
1874-75), Dafla Hills, Assam. 
Four specimens in my collection. 
