OF DENISON UNIVERSITY. 
27 
logical Siirv. Neb., p. 193) in the figure of Geinitz, the dissimilarity 
in form is very slight and it is suspected a wider comparison would 
prove these shells identical. 
Aviculopecten sorer, sp. n. ? 
(Plate I, Fig. 7, and Plate III, Fig. 16.) 
We have a number of specimens of a fine species remarkable for 
the beauty of the surface markings, but all too imperfect to very satis- 
factorily characterize. The form, exclusive of the ears, is sub-trian- 
gular, both anterior and posterior margins being concave or nearly 
straight. The greatest breadth is below the middle and the lower 
margin is a uniform, rather shallow curve. The ears are large and 
sub-equal, the anterior are (?) most acute. Shell ornamented with 
prominent distant ribs separated by three or more smaller ones, all be- 
ing nodose in the path of concentric markings or, rather, the nodose 
character produces the effect of concentric lines crossing the striae. 
This shell resembles A. scalaris in general configuration very closely, 
more closely than indicated by the description, but it seems to vary 
greatly. The nodose character is also variable. No perfect specimen 
has been found, but many fragments indicate a species about the size 
and form of A. scalaris, with rounded distant striae, separated by 
crowded finer ones. The ears are broken in all the specimens seen, 
but we presume the valve. Fig. 16, Plate III, is opposite to that of 
A. scalaris Fig. 8, Plate I, and so there is a slight difference in 
outline. 
Aviculopecten sp? 
(Plate I, Fig. 6.) 
A little shell similar in outline to A. (Crenipecten) leon, Hall, is 
known from the single valve figured. It is peculiar in the relatively 
very short hinge and restricted ears, as well as in the ornamentation 
which consents of sharply defined, though small, ribs arranged in 
rather distant pairs. The specimen is a left valve and rather oblique. 
The general outline is acutely ovoid, the beak being nearly central and 
quite prominent. The posterior ear is very small and acute, anterior 
ear larger, with a more concave outline. 
