320 MEMOIRS OF THE CARNEGIE MUSEUM 
River, at Warren, Pa. The figure here given (fig. 7) is a reproduction of this 
sketch. It represents a shell as seen from above, with its hind portion turned 
up. Allowance must be made for the difficult conditions, under which this sketch, 
which is rather diagrammatic, was made. 
The general shape of the lamella and flap in ZL. ventricosa, is ribbon-like, 
much longer than wide, and the free anterior projection is rather long. It arises 
rather suddenly at the posterior end near to and immediately in front of the 
branchial opening, forming there an angle, at which the eye spot is situated. The 
edge of the ribbon (inner edge of mantle) is, when expanded, rather smooth, but 
there are, chiefly toward and at the free anterior lobe, a few irregular teeth, which. 
give to this lobe a lacerated appearance. These teeth are quite variable. When 
contracted, the edge is wrinkled and crenulated, and the free lobe is much shorter, 
triangularly pointed or rounded off. Immediately in front of the lobe, the inner 
edge has a few small teeth, or it is scalloped, and becomes smooth anteriorly. 
This peculiar lamella or flap is also distin- 
guished by its color. In L. ventricosa it is gray 

on the outside; on the inside it is a beautiful 
Fie. 8. Lampsils ventricosa, (Barnes), fe- ale orange, with a blackish longitudimal/ aime 
Ee pe rear pe ea a iu (See fig. 8). The thickened margin of the man- 
tle between the inner and outer edge is also pale orange, or light brown, with 
black mottlings. Together with the eye spot, mentioned above, and with the 
whitish marsupium with its black markings on the edge, being visible between 
the flaps, the whole aspect of these parts in the living shell in this condition becomes 
rather attractive. 
In the male the lamella and flap are similar, but smaller in all dimensions, the 
colors are less sharply defined, and the free lobe is very small, yet distinctly present. 
Practically the same apparatus is seen in L. ovata, multiradiata, and cariosa, 
only in the two latter species the teeth of the edge are more numerous, and the 
black line is often missing in LZ. ovata and cariosa. Altogether there is much 
variation in the intensity of the color, the light parts shading from deep brown to 
light orange. The eye spot is always present in the female, but indistinct in the 
male. In alcoholic material, of course, the colors largely fade. 
In L. orbiculata the same flap as in L. ventricosa is developed quite typically; 
in alcoholic material a distinct black line is seen, and between this line and the edge 
the flap is rather dark black. The only difference is that here the teeth along the 
edge are more numerous and more crowded, increasing in size in the postero- 
anterior direction. L. orbiculata generally is placed with L. ligamentina in the 
