9 
LEPTiENA, Dalman. 
Objections have been so strongly urged against the name 
Productus, that we have found it necessary to adopt Dal- 
man ’s name Leptaena for this genus. It is characterized 
by the hinge-area in each valve extending the whole width 
of the shell, and by the margins of the valves being pro- 
duced together beyond that part of the shell which contains 
the animal, and bent down so as to form a kind of inverted 
cup. The flatter (lower) valve has no projecting beak, 
but in the middle of its hinge-line is a process which nearly 
fits the aperture in the convex deltidium of the other valve, 
which slides upon it as it opens or closes; this process 
is divided within into two diverging teeth. The same 
valve has a smaller longitudinal septum in its middle, be- 
tween the muscular impressions. The beak of the (upper) 
convex valve is in some species produced considerably. 
All the species have striated surfaces, and many have long- 
spines, often tubular, on the outside, and numerous little 
spine-like projections within. 
LEPTiENA anomala. 
TAB. DCXY. — -Jig. 1. 
Spec. Char. Irregularly triangular, elongated, com- 
pressed, striated; beak very much produced, its 
sides spinose ; hinge-area large, triangular. 
Syn. Pinna inflata. Phillips, Geol. Yorks. Part II. 
21 L PL VI. f 1. Mytilus striatus. Fischer, 
Orycht. Mosc. 181. Pl. XIX. f. 4. 
A very irregular and often distorted shell, with a surface 
and texture precisely similar to that of Leptccna scabricula 
and the other species of the genus. 
Individuals rarely occur separate: they are commonly 
distoi ted, broken, and imbedded one in another, which 
i \ ifficult to comprehend. The spines 
near the hinge are small, they are best defined in fig. a.; 
their bases are seen on the internal cast (fig. d.). Figs’, 
bb. are two views of one specimen, which shows the large 
area beneath the beak, an approach to which is seen at fig-. 
3 b. Those found in Russia are often much larger and 
less elongated, therefore more resembling the ordinary 
form of Leptsena. The specimen represented at fig. 1 c, is 
in Mr. Gilbertson’s cabinet ; it is from the mountain lime- 
stone of Holland. I am not acquainted with the localities 
of the others. 
Von. VII. c 
