246° * PALEOZOIC PALEONTOLOGY. 
M. mytiliformis Foerste, and it is therefore considered as cogenerie 
with them. The prominent beak is terminal, and from it an angular 
umbonal ridge, becoming rounded posteriorly, extends obliquely to 
the postero-ventral angle of the shell. From the umbonal ridge to the 
dorsal and posterior margins the surface of the shell is convex; antero- 
ventrally the slope is abrupt and nearly vertical to the margin. 
The dimensions of the type specimen are: extreme length from the 
beak to the postero-ventral angle, 34 mm.; greatest width at right 
angles to the above line, 20 mm.; greatest convexity, 10 mm. 
Remarks.—This species resembles M. mytiliformis Foerste more 
closely than any other member of the genus, but the shell is more 
oblique, with a more obtuse beak and with a much more abrupt slope 
from the umbonal ridge to the antero-ventral margin. 
GONIOPHORA sp. undet. 
Description —Al] the specimens of this species which have been 
observed are imperfect, so that its characters cannot be determined 
with certainty. It is a sharply-carinate, oblique shell, with an in- 
curved beak. Dorsally from the carina the shell surface is convex 
and ventrally it is concave. In no specimen is the outline of the 
shell complete, but the depth of each valve is apparently greater than 
the height of the shell. The length of the best-preserved valve, al- 
though imperfect, is 16 mm., with a height of 5 mm. and a depth of 
7 mm. These dimensions, however, probably do not correctly repre- 
sent the dimensions of a perfect shell. 
JASTROPODA. 
STRAPAROLLUS sp. undet. 
Plate XXIL., Fig. 14. 
A single imperfect specimen has been observed in the lower beds 
of the Decker Ferry formation, which is referred to the genus Stra- 
parollus. It has a diameter of 25 mm., with four or five volutions,. 
