224 Thirty-fifth Keport on the State Museum. 



height. The alae and the ornamentation of the test are distinguishing 

 characters. 



Formation and locality. Hamilton group, Schoharie, N. Y, 



AVICULOPECTEN FASCICULATUS. 



Aviculopefiten fasciculatus, Hall. Pal. N, Y., vol. v, pt. 1. Plates and Explana- 

 tions : PI. 5, figs. 9, 10, 12, 16, 17. Jan., 1883. 



Aviculopecten repletus, Hall, Pal. N. Y. , vol. v, pt. 1 . Plates and Explana- 

 tions: PI. 5, figs. 13-15. Jan., 1883. 



Avicuhpecten Orestes, Hall. Pal. N. Y.,vol. v, pt. 1. Plates and Explana- 

 tions : PI. 5, fig. 11. Jan., 1883. 



Shell obliquely and transversely ovate ; height more than seven- 

 eighths of the length, produced behind ; pallial margins regularly 

 rounded, becoming more convex toward the middle of the postero- 

 lateral side, and extending in a straight or slightly concave line to 

 the beaks. Valves moderately convex, the right one more depressed 

 when seen in connection with the other, shorter and comparatively 

 less oblique. Hinge-line straight; length nearly two-thirds the height 

 of the shell ; -extending in young individuals as far as the anterior 

 margins. Beaks prominent, well-defined, situated anterior to the mid- 

 dle of the hinge-line. Umbo very convex. Ears of the left valve 

 triangular, the posterior one larger, more attenuate at the extremity, 

 and defined by a sulcus ; the margins concave from the rapidly sloping 

 side of the prominent umbo. Ears of the right valve much nar- 

 rower, and attenuate at the extremities, with fewer radiating lines, 

 marked by a very deep byssal sinus. 



Test ornamented with numerous filiform, radiating striae, which 

 are often fasciculate, and fine concentric lines of growth. The broad 

 fascicles of striae often extend across one interval of growth, and on 

 the succeeding interval appear as regular or irregular striae without 

 aggregation, or as fascicles of finer striae. In young specimens the 

 rays are regular, with a slight fasciculate arangement. The concen- 

 tric lines are sharper and more crowded on the ears and the rays are 

 more subdued. 



One specimen has a height of 30 mm., and a length of 32 mm. ; 

 another specimen has a height of 23 mm., and a length of 25 mm. ; 

 the hinge-line is 16 mm. 



The form and surface markings distinguish this species. It differs 

 from A. formio, A. princeps and A. pecteniformis in its surface mark- 

 ings ; and from A. princeps especially, by the presence of radii on the 

 wings. 



