386 PROCEEDINGS OF THE NATIONAL MUSEUM. tol. 42. 



ties of hinge rounded, angle between umbonal ridge and hinge margin 

 about 50°. Anterior slope convex, no indication of mesial sulcus. 

 Surface nearly smooth, a few obscure concentric wi'inkles of growth 

 are seen over the outer half of the shell and well-preserved shells 

 show faint, irregular, fine, concentric lines. 



Size variable, but rarely over 1 iach in length; the large majority of 

 specimens are from one-tiaK to three-fourths of an inch long. 



Interior molds occasionally show a distinct anterioi; muscular scar, 

 but in no specimen has the outline of the posterior scar been traced. 

 The anterior scar is strongly impressed, situated at the extreme 

 antero-cardinal angle below the hinge, and is bounded by a short, 

 strong ridge on the inside. Pedicel scars are frequently seen on the 

 area between the posterior edge of the anterior muscular scar and the 

 bottom of the cavity of the beak. On the anterior side of the umbonal 

 cavity three small, oval pits are seen near the apex and occasionally 

 a fourth half way down toward the anterior adductor. 



The cardinal margin in most specimens exhibits little else than a 

 slight thickening of the edge of the very fragile shell. In a few 

 specimens trace of a small oblique thickening of the hinge is seen 

 under the beak of left valves and on right valves a somewhat broader 

 thickening, which perhaps represents two teeth between which the 

 right topth fits. In fnost cases the lateral hinge margins are too 

 narrow for the exhibition of any distinct lateral teeth, and the valves 

 are separate in fossiHzation, although there are many cases of attached 

 valves. 



Dimensions of the type-specimens. — (1) Length 22 mm., height 15 

 mm.; (2) length 19 mm., height 14 mm.; (3) length 23 mm., height 

 15 mm.; (4) length 19 mm., height 14 mm. 



Locality. — The typical locality is in the shales on Moose Island at 

 Shackford Head and on the shores of Broad Cove, where the species is 

 found in great abundance with rarely any other fossil species except 

 Lingulas and ostracods. 



Coty pes. —C&t. Nos. 58431 to 58433, U.S.N .M. 



EXJRYMYELLA SHALERI, var. BREVA, new variety. 

 Plate 49, figs. 5, 6, and 7. 



Form and general characters as in E. sJialeri, but the height is 

 nearly as great as the length, with correspondingly more erect mnbonal 

 ridge. 



The proportions of three typical specimens are: (1) Length 15 mm., 

 height 14 mm.; (2) length 16 mm., height 15 mm.; (3) length 16 

 mm., height 14 mm,; and the umbonal angle is 55° to 65°. 



Locality. — Same as the typical forms of the species. 



Cotypes.—C&t. No. 58434, U.S.N.M. 



