t^^l

192 irsiONiDiB.
stria;; dorsal margin anteriorly gradually sloping, posteriorly
arched and more rapidly descending; ventral margin somewhat
straight; anterior side rounded; posterior side angled above and
below, somewhat obliquely and obtusely rostrate; hinge teeth
Fig. 24.—1 .& 2. Lamellidens (L,) maimoarmgi, Preston. (Type.) Nat. size.
3. Hinge of same.
well developed, moderately short; anterior adductor scar deeply
impressed; posterior scar somewhat roughly triangular, well
impressed; interior of shell bluish iridescent, rather granulate.
Long. 25-5, lat. 50 mm.
Hah. Siliguri; there are also specimens in the Indian Museum
from Namtsik, Dihong Eiver.
Type in the Indian Museum.
A small, light, and thin form, which Simpson in his ' Synopsis
of the Naiades ' * refuses to recognise as a species, but regards as
L. consohrinus; the author, however, having Ijeen able to examine
a large series from the collection of the Indian Museum, all the
specimens of which are very constant in their size, form, and
hinge, and other characters, considers it without doubt to be
worthy of specific rank.
The following dimensions are taken from specimens in the
Indian Museum Collection :—
Lat
1.
. .. 22-25
... 41-75
11-75
2.
21
40-5
12-6
3.
29-5 mm.
37 mm.
9-25 mm.
* Washington, D.C., Smiths. Inst., Nat. Mus. Proc. xxii, 1900, p. 856
{footnote no. 3).