64 Description of a New Genus of Fresli-water Bivalves. [Feb. 
of the foot and shell. Syphons separate, as long as the shell, when fully extended!; 
the anal one, or that nearest the hinge, half the thickness of the other ; apertures 
constricted, not ciliated. 
Inhabits the Jumna, Gumti, and Ganges. 
When I first discovered this shell, I was induced, from its lengthened form and 
gaping extremities, to suspect its affinity to the Solcnaceos, but the bad state of the 
deserted shells which I found, in which the sharp, delicate teeth were worn down 
to slight tubercles, which appeared of little importance, and the semi-internal liga- 
ment induced me to refer it, provisionally, to Anodonta , accompanied only by a 
mark of doubt. The teeth are so delicate "that they are only to be found in the shell 
when taken with the animal, and the slightest cleaning breaks them down. 
The shell is generally open as wide as the mantle and the epidermis (which is 
folded over the edge of the shell, and is soldered to the mantle) will permit. I placed 
between 40 and 50 live shells in a tub of water, with a piece of strong slaty clay, but 
none of them attempted to perforate it, possibly on account of its hardness, although 
kept for several days. The animal at times spirts a strong stream of water from 
the anal syphon. It inhabits cylindrical holes in clay, which it probably excavates 
with its powerful foot, which is always downwards. The holes descend to the depth 
of half a foot and more. 1 should not consider the shell, the extremity of which is 
defended by the lapping over of the epidermis, as sufficiently strong to aid in any 
way, except as a fulcrum for the operations of the foot. They are found by digging 
below the surface of the water, in the margins of banks, where they appear to 
have been perforated. 
The worn shells are not uncommon in the beds of the Jumna and Gumti, wken 
the waters are retiring. They are rarely found in holes in cancar rock. In this 
case the shell is distorted, if confined in an irregular hole, to the sinuosities of which 
it, in a measure, conforms itself ; thereby shewing that the residence was chosen 
accidentally, and that the abode was not formed by the animal itself. In the clay 
the shells are more symmetrical. 
As in the Solenncece, the edges of the mantle are soldered together at the base, 
forming a tube which confines the animal, and gives more support to its muscular 
foot, the exertions of which are principally required in the direction of the axis of 
the shell. In its habits, Novuculina also resembles Solen , clay being mei’ely substi- 
tuted for sand, in which the latter genus delights to burrow vertically. The animal 
differs from Solen, in having its syphons free, instead of occupying a common tube; 
and in having an expanded, instead of a conical, termination to the foot. 
To Solen Ensis the shell seems, at first, to have little resemblance ; but it has more 
characters in common with Solen Legumen, which is less linear, and has compara- 
tively prominent beaks situated towards tlie centre of the hinge, -margin. In Solen 
Legumen , also, the ligament, although external, has like our fluviatile shell, a chan- 
el (not mentioned by Lamarck), communicating with the interior of the shell : and 
it appears deserving of forming a separate genus intermediate between Solen Ensis, 
and its affinities, and the genus under consideration. 
Our shell is easily distinguished from the Sole ns which most nearly approach to 
it by its prominent beaks, its irregular form, and the great length of its sypbonal 
scar. At times some of the teeth become obsolete, as iiCSolen ; and both the cardin- 
al and basal edges are subject to slight emargination . 
Long before meeting with the live animal, I had predicted the extraordinary length 
of the syphons from the appearance of the sypbonal scar, which, as Mr. Gray has 
well observed, in the Zoological Journal, is a good auxiliary character for the clas- 
sification of bivalves. 
Except Mr. Gray s new Chinese genus Glauconome , no other fresli-watpr shell 
has a long sypbonal scar. The remaining Conches Fluviatiles , and the whole of the 
Naiades having but a slight emargination in the submarginal impression, and their 
eihated syphons scarcely projecting beyond the extremities of the shells. 
This shell is chiefly interesting as being the first of the family of Solenacea, or 
even of the Crassipeda, which has been ascertained to inhabit fresh water, and must 
be peculiarly so to the geologist, who can ill pronounce upon the nature of the me- 
“ which was inhabited by a fossil shell under investigation, until all the genera 
vv ich inhabit fresh water are known. 1 must confess, however, that it has appeared 
to me, that in geology too much stress has been laid upon shells, and that the water 
nc i deposited them has often been hastily assumed as fresh, from the examina- 
ion o ti;e exuviae found in a particular stratum, to which currents and other ex - 
raneous causes might easily have conveyed them from some vast antediluvian river. 
