248 Thirty-fifth Report on" the State Museum. 



face. Usually the test; shows ouly the strong rays, with occasionally 

 a reticulation where the concentric folds are only partially preserved. 

 The figure cited represents also the internal mould where the 

 test has been wholly removed. Ligamental area, in young shells, 

 represented by a slight inflection of the margin of the hinge with 

 a very small longitudinal groove. In more mature specimens this 

 area is wider, the number and strength of the grooves increasing, 

 until they occupy a continuous space between the extremities of the 

 hinge-line, slightly bending outward at the beak ; the inner ridges 

 and grooves do not extend the whole length of the area. Cartilage- 

 pit and muscular impressions not observed. 



The original specimen of this species is 38 mm. high, 39 mm. 

 long, hinge-line about 30 mm. Another more nearly entire speci- 

 men is 35 mm. high, 37 mm. long, hinge-line 30 mm. The largest 

 specimen observed shows a height of 78 mm., with length nearly 

 equal, and hinge-line 42 mm. in this specimen the longest diame- 

 ter is 85, mm. , measured from a point on the upper anterior margin 

 to the lowerposterior margin. 



This species is distinguished by its form and surface markings. 

 The characters of surface distinguish it from L. Priamus and L» 

 macrodontus, though in form it bears some resemblance to the former ; 

 and in the ligamental grooves it is similar to the latter. Pterinopecten 

 suborbiciclaris, in some of the younger specimens, resembles this species 

 in general aspect ; but none of that species have shown a broad, liga- 

 mental area, and the ears continue to increase with the growth of the 

 shell. 



Formation and localities. In shales of the Hamilton group at 

 Monteith's Point, Oanandaigua lake, Ontario, county ; Moscow, 

 Geneseo and York, Livingston county; and in the shale and Encrinal 

 limestone, along Lake Erie shore, Eighteen-mile creek, Erie county, 

 K Y. 



Lyriopectek interradiatus. 



Lyriopecten interradiatus, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Ex- 

 planations : PI. 2, figs. 1-4. Jan., 188?. 



Shell large, longitudinally very broadly elliptical * transverse axis 

 somewhat oblique to the hinge-line; height about one-ninth less 

 than the length ; margins full and regularly rounded. Valves 

 about equal in dimensions. Left valve depressed, moderately con- 

 vex. Eight valve flat, or slightly concave below, becoming convex 

 toward the beak. Hinge-line straight, central to the body of the 

 shell ; length less than two-thirds the longitudinal diameter of the 



