14 PALAEONTOLOGY OF NEW YORK. 



•Jn mill. Aimtlicr iinli\ idiial liiis a lu-ight iiml length of 27 iimi., and liinge- 

 liui- 111 nnii. 



This species differs from A. fasciculatus m its comparatively larger anterior 

 and smaller posterior ears, uliile the shell is less full hehiiid, and the fasciculate 

 surface has not l»een observed. In A. formio the posterior ears are much 

 larger, and the surface is distinctly reticulate. In A. scahridus the beaks are 

 more rounded, the wings more extended, and the surface quite diflerent. Some 

 forms of A. duplicatus and A. rugastriatus resenililc this species ; but the posterior 

 eais of those species are larger, the anterior \yA\v wider, and the surface 

 markings characteristic. 



The specimen, figure 13, plate 7, from the Chemung group is very nearly 

 related to this species. A careful examination reveals the following difter- 

 ences. A. Itys is less oblique in outline, radiating striae less distinctly rounded, 

 inclining to angular, distance between them greater than the striaj themselves ; 

 the evidence of the ini])lantation of intermediate striae is obscure ; the 

 concentric lines are more distant and sharper, leaving the radii in the cast 

 distinctlycrenulate. 



Formation and localities. In the Hamilton group at Fultonham, Schoharie 

 county ; shore of Cayuga lake ; and Darien, Genesee county, N. Y. 



AVICULOPECTEN LAUTUS. 

 I'LATE ni, ?"u;s. ii;, it. 



Avituli)j>etten laittus, Mai.i,. 1'jiI. N. V., vol. v, ]it. 1. I'latf.s ami Exiiliuiiitidii.s : PI. 3, fig^s. IG, 17. 



Jjiii., 1S83. 



SnEi.i. oliiiqucly o\atc, height e(jual to till' length, valves depressed, convexity 

 of right and left valves sub-equal. 



Hinge-line straight, length about one-fifth less than tlie height of the 

 sliell, or in some specimens longer, extending as far as the anterior margin 

 of the valve. Beaks depressed, obtuse, anterior to the centre of the hinge- 

 line. 



Ears sub-equal, triangular, flat, nnicronate at the extremities, margins 



