52 
BULLETIN OF THE LABORATORIES 
a deep byssal sinus and steep upibonal slope. Length of left valve 
i6 mm; width 15 mm; length of hinge 10-12 mm. 
Nodule layer, Moot’s run. Collection of W. F. Cooper. 
Aviczdopeoten (Cf. oiueni, M. and w.) 
fPlate III, Fig. 5.) 
Shell small, subcircular, lower margin nearly equally curved to 
points nearly half way to the beak, here suddenly flexed to meet the 
lateral margins, the anterior one in the left valve being slightly con- 
cave, the posterior a little convex; beak prominent; hinge line some- 
what less than the width ; anterior ear rather large, obtusely angled ; 
posterior ear smaller and more acute and rather less sharply defined ; 
surface quite convex, greatest convexity being about one-third from 
the beak, ornamented by rather numerous bifurcating and implanted 
striae, of which about fifty can be counted on the body of an average 
shell. Length 10 mm; width 10 mm; length of hinge 8 mm. The 
difficulty of comparing this species with A. oweni is increased by a 
doubt as to which valve is figured by Meek and Worthen. The de- 
scription states ‘‘right valve unknown,” while the figure is stated to 
be that of the right valve. If it be a left valve and our own are like- 
wise left valves, the relation of the ears is reversed. Our species is 
smaller, but otherwise resembles the Illinois form. None of the spe- 
cies quoted by Winchell as from the Waverly and its equivalents, 
seem to be identical with this, though it may prove the young stage of 
one of the common ones, perhaps A. winchelli. The horizon is the 
same as in that species, the free-stone of middle Waverly. 
Aviciilopecten ( Crenip&cten) newarhensis, Win. ? 
(Plate III, Fig. 31.) 
A single right valve may belong to this species as indicated by its 
rather narrow form. As Winchell’s specimens were all left valves, the 
identification can only be conjectural. Length 18 mm; width 15 mm. 
Valve very flat, covered by irregularly alternate, rather filiform striae. 
Umbonal slopes about 90° or less. 
