50 BULLETIN OF THE LABORATORIES 



a 



are at a loss for any sufficient distinctions between onr 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^atus, sp. n. 



Left valve extremely elongate, narrow and quite convex along 

 the longitudinal axis. Height to length of body as i^ 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 ofR-'red except thai the form is so unlike that of any known 

 species as to make it unmistakable. Perhaps A. dissimilis FL, as iden- 

 tified by Toula, 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 =5 mm. Number of striae 

 in one mm, 3 at the lower margin. 



Freestone of middle W.iverly. 



Avlculopecfen {granvillensis , ^p n ) 

 (Plate X, Figs. 8; Plate XII, Fig. 11.) 



Cf. Aviculopecten ainplus 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. 



