344 PR0CEEDIN08 OF THE NATIONAL MUSEUM. vol.45. 



in an acute point. Ear smaller than the wing. Surface of body of 

 shell covered by fine rounded radii, which in larger shells cease 

 before reaching the ventral margin and are wanting on the ear and 

 wing, crossed by fine concentric lines and coarse wrinkles, which 

 become lamellose upon the wing and ears, and in full-grown specimens 

 along the ventral margin form there a band of sometimes 3 or 4 mm. 

 width, upon which the radii cease. 



A small specimen (pi. 30, fig. 21, magnified) is referred to this 

 species. It appears to possess all the characters of the larger speci- 

 mens shown on the early stage of their growth, except that on the 

 anterior slope of the body the radii extend faintly across the sulcus 

 of the ear, but are not present upon the main area of the ear or upon 

 the wing. 



Dimensions of the type specimens (pi. 30, fig. 20) : Length of hinge, 

 19 mm.; length of body from hinge to ventral border, 20 mm.; from 

 tip of beak, 22 mm.; from end of anterior ear to postero-ventral 

 angle, 23 mm.; width across center of shell, IS mm. Young speci- 

 men: Greatest width at hinge, 9; at middle of shell, 8^; from hinge 

 to front, 9; from tip of beak, 11; tip of ear to post. vent, angle 

 11^ mm. 



Formation and locality. — ^Pembroke formation at head of Leighton 

 Cove, Pembroke, Maine (loc. No. 5.3.8M2). 



Cotypes.— Cat. No. 58966, U.S.N.M. 



Genus GRAMMYSIA Verneuil. 



GRAMMYSIA PEMBROKENSIS, new species. 



Plate 31, fig. 2. 



This species from the purple sandstones of the upper part of the 

 Pembroke formation is similar to G. cingulata Hisinger of the Upper 

 Silurian of Great Britain. It differs from the figures of that species 

 given by Salter ^ in its narrower more transverse form and the more 

 angular anterior termination of the cardinal angle. In size it is 

 smaller, and our specimens show only a single furrow on the left 

 valve. The dimensions of our figured specimen (Cat. No. M1238) 

 (which is a mold, the figure having been drawn from a wax impression 

 of the specimen) are greatest transverse length 32 mm., across the 

 shell perpendicular to hinge line from termination of sulcus to the 

 cardinal margm 12^ mm. The figure is slightly enlarged. A second 

 specknen of the same form (Cat. No. M1303) is 36^ mm. long; it is 

 extended farther forward of the sulcus than the first specimen. A 

 thu-d specimen (M1303.2) a left valve is 31^ mm. long transversely, 



» Mem. Geol. Surv. Great Britiau, vol. 2, pt. 1, 1848, pi. 17, figs. 1, 2. 



