t^^l

NODTJLAEIA. 137
A very widely spread form, as will be seen from the list of
localities quoted above ; to a certain degree it varies considerably;
always eorrugatedly sculptured in the umbonal region, this
character may be either restricted to the extreme umbone, or
spread over the greater portion of the surface of the shell.
A number of so-called species have been constituted out of its
many varietal forms, of which, perhaps, that most often quoted is
U. leioma, Benson, but on examination of a large series there can
be no doubt that these must be relegated to sjnonymj'.
Below are given the measurements of four specimens in the
Indian Museum, No. 1 being from Calcutta, No. 2 from Bagh,
No. 3 from TJmbaila, and No. 4 from Poonassa.
1. 2. 3. 4.
Long 20 17-25 25-25 30 mm.
Lat 39-75 30 49-5 56 mm.
Diameter 12 11 18-75 21 mm.
Var. gaudichaudi {Eydoux).
Unio qaudichaudi, Eydoux, Mag. de Zool. 1838, CI. v, p. 10,
pi. Yl8,6g.3.
Maryaron (JJnio) gaudichaudi, Lea, Svn. 1860, p. 32; 1870,
p. 50.
Nodularia gaudichaudi, Simpson, Washington, D.C., Smiths. Inst.,
Nat. Mus. Proc. xxii, 1900, p. 812.
Shell oval, transverse, inequilateral; umboues not prominent,
slightly roughened, covered with a periostracuni; the anterior side
is short and rounded; the posterior is broader and obscurely angled;
the whole shell slightly SYS-oUen; texture of shell thin, finely or
irregularly striate and covered «ith a dirty brown or j'ellowish
periostracum ; interior of shell nacreous, of a pinkish violet
shade ; hinge very narrow and nearly straight, a single, rough and
projecting cardinal tooth appearing on the right valve and two
oblique and unequal cardinal teeth in the left valve; lateral teeth
very thin, smooth, obliquely truncate at the posterior end, the
plates of the opposite valve, between which it fits, of nearly equal
size.
Long. 22-5, lat. 38-25 mm.
Hah. Rivers of Bengal.
Yar. keraudreni {Eydoux).
Unio keraudrmi, Eydoux, Mag. de Zool. 1838, CI. v, p. 8, pi. 118,
fig. 1.
Margaron (Unio) keraudreni, Lea, Syn. 1852, p. 30; 1870, p. 46.
Shell obJong-ovate, somewhat depressed, very inequilateral,
smooth; anterior side obtuse, short; posterior side gently
attenuated with blunt extremity ; umbones scarcely prominent,
much eroded ; remainder of outer surface covered with a dark
brown periostracum; interior of shell nacreous and tinged with