14 
MELANIA, sp. 
There is among the shells collected by Mr. Mouhot a turrited 
species of this genus ; its chief character consists in the under margin 
of the whorls being swollen and prominent over the following suture, 
in the same manner as in Twrritella imbricata, Lam. The shell 
is of a uniform olive-green colour, which becomes in the uppermost 
whorls reddish: it is provided with rather strong vertical strie. 
As Mr. Cuming tells me that he has sent specimens of it to Mr. 
Reeve to be described and figured in one of the next numbers of the 
«Conchologia Iconica,’ I do not give it any specific name. The same 
is the case with the two following species. 
MELANIA, Sp. 
A turrited shell with large dark-brown stripes, a little shorter than 
the preceding, allied to M. testudinaria, Busch, and M. picta, Hinds. 
Leg. Mouhot. 
MELANOPSIS HELENA, Mouss. 
Leg. Mouhot. 
NERITINA MELANOSTOMA, Troschel= Neritine indienne, Eydoux 
et Souleyet, Voy. Bonite, 34, 32-35. 
Mr. Reeve is wrong in uniting this species with N. crepidularia, 
Lam., from which it differs in the narrower form of the mouth and 
of the whole shell, and in the blackish colour of the inner lip. 
NAIACEA. 
A considerable number of species of the genus Unio, found in Siam 
by Dr. House, are described by Lea in the sixth volume of his ‘ Ob- 
servations on the genus Unio,’ 1857. Several of them are in the col- 
lection of the British Museum, sent by Sir R. Schomburgk. 
Unio novset, Lea, /. ¢. pl. 23. f. 3. 
This is a flat shell, with a small wing before and a large one di- 
stinctly folded behind the summits. Three specimens of different 
ages, sent by Sir R. Schomburgk, render it highly probable that 
U. myersianus, Lea, 1. c. pl. 22. f. 2, is merely the adult of the same 
species, the wings being gradually lost with age. 
Leg. Sir R. Schomburgk. 
Unio cravinus, Lea, /. c. pl. 24. f. 5. 
Is a very distinct form, not yet known from the Eastern hemi- 
sphere, similar to U. capae from North America; the wing, never- 
theless, shows some wrinkles at its base, which are elevated and 
anastomosing, as in many of the Eastern species. 
Lao in Siam ; leg. Mouhot. 
Unio rvusticus, Lea, /. e. pl. 25. f. 7. 
As I am not quite confident in identifying our shell with that de- 
scribed by Lea, I shall add a diagnostic phrase. 
