50 
BULLETIN OF THE LABORATORIES 
V 
are at a loss for any sufficient distinctions between our form and the 
species quoted. A large species of Athyris is also found in the no- 
dules at Moot’s run, which apparently differs from the one quoted. 
The resemblance between the Devonian and carboniferous members 
of this genus is too close to make a separation easy at present. 
The small species Figs. 19, 34, Plate VII, may be an Athyris or 
an Amphigenia resembling A. elongata. Congl. I. The affinities of 
Fig. 21 of the same plate are still more obsure. 
Aviculopecten perelon^atiis, sp. n. 
Left valve extremely elongate, narrow and quite convex along 
the longitudinal axis. Height to length of body as to i. Body 
acutely narrowed toward the curved beak, the sides forming an angle 
of less than sixty degrees. Posterior wing small, triangular, rather 
acute. Surface marked by very numerous crowded, hair-like, sharp 
striae, which bifurcate and increase by intusuception irregularly, also 
by concentric folds, which are more distinct toward the sides. The 
wings have less numerous radiating striae. The convexity of the valve 
is greatest near the middle and forms almost a fold along the longitu- 
dinal axis, sloping regularly to either margin. The umbonal slopes 
are both concave and rather abrupt. 
Such a brief description of a single imperfect valve would not 
have been offered except that the form is so unlike that of any known 
species as to make it unmistakable. ' Perhaps A. dissimilis FI., as iden- 
tified by ToLila, from Spitzenbergen, approaches it most nearly in out- 
line, though our species is much more elongated. It does not appear 
possible that the peculiarities can be to any extent due to distortion. 
Length 24 mm, width 15 mm, posterior ear mm. Number of striae 
in one mm, 3 at the lower margin. 
Freestone of middle W.iverly. 
Aviciilopecten {graiivillensis, n.) 
(Plate X, Figs. 8; Plate XII, Fig. ii.) 
Cf. Aviciilopecten amplus and A. crenistriatus. 
An imperfect left valve and fragments of a right valve suggest 
very close relationship to A. amplus of the Keokuk of 111 . 
