Foerste.] 
316 
[May 1, 
more rounded postero-lateral angles, the strongly incurved beak of 
the ventral valve, the strong concentric striae, and the slightly 
stronger radiating striae. 
Atrypa nodostriata , Pal. Ohio, Vol. n, PI. vn, figs. 12-14, is a 
cast from Yellow Springs, Ohio. It is rather gratuitous labor 
to refer it to any distinct type, but its more rounded postero-lat- 
eral angles, the somewhat coarser radiating striae, and the fact that 
the muscular impressions of the ventral valve are not so elevated but 
that the beak may have been incurved over the dorsal valve, make it 
possible that the shell may have belonged to a variety of A. mar - 
ginalis. It is evident that casts of the exterior are necessary to 
determine the relationship of this form. 
Atrypa marginalise var. multi-striata var. nov. Under this name 
is placed a single specimen from Hanover, Indiana (Plate iy, 
fig. 8). It is 9.1 mm. long and 9.8 mm. broad. It differs from 
the species already described in the larger angle, about 40°, formed 
by the sides of the sinus, and in the much finer radiating striae, of 
which eight and one half to ten fall in a width of 4 mm. The pos- 
tero-lateral angles are also somewhat more angular than in most 
specimens of the species, and the concentric striae corresponding 
to the finer radiating striae, take an intermediate position between 
those of the species and the variety imbricata , about seven or seven 
and one-half occupying a length of 4 mm. Its affinities are appar- 
ently nearer to the typical forms of the species. 
Rhynchonella Janea, Billings. 
(plate v, FIGS. 23, 24.) 
At Collinsville, Alabama, casts of a species of Rhynchonella are 
found in great abundance. Young specimens have both valves 
moderately convex, the convexity increasing with age. In speci- 
mens 7.5 to 8 mm. long and 9 mm. broad the thickness is 3.6 mm. 
In specimens 9 mm. long and 9 mm. broad, the thickness is 
6 mm. In specimens 10 mm. long and 11.3 mm. broad the thick- 
ness may be as high as 9.2 mm. As a rule the dorsal valve is 
more evenly convex than the ventral, the ventral valve near the 
centre appearing slightly flattened on account of the elevation at 
that point of the lateral lobes above the sinus. The apical angle 
varies from 80° to 90° the more obese specimens usually showing 
the higher angle. The mesial fold has four plications as a rule, 
and the mesial sinus contains three plications. Frequently the 
