LAMELLIBRANCHIA TA. 
299 
the sinus is marked by strong, elevated, radiating striae, which dominate 
the concentric striae. The test is raised into a crest along the umbonal 
ridge, especially in the posterior half of its length. 
Anterior muscular impression large and deep, situated close to the anterior 
margin, truncated posteriorly by a strong ridge or clavicle. Pallial line 
parallel to and near the basal margin, appearing as a shallow groove, recurv¬ 
ing near the post-basal extremity and terminating in a broad, muscular 
impression, the anterior margin of which is near the center of the length of 
the shell. 
A specimen of medium size has a length of 54 mm., and a height of 23 
mm. A somewhat smaller individual measures 50 mm. in length and 20 
mm. in height. 
This species is very closely allied to G. perangulata of the Schoharie grit, and 
it is possible that they are identical. In the specimen fig. 3 of plate xl, the 
hinge-line is shorter than in specimens of G. perangulata, but the compara¬ 
tive length of the hinge-line appears to be variable in the two species. Other 
differences are pointed out under the description of that species. 
Formation and localities. In the shales of the Hamilton group, on the shores 
of Cayuga and Skaneateles lakes, at Delphi and Pratt’s falls, Onondaga 
county, N. Y. 
Goniophora Glaucus. 
PLATE XLIII, FIG. 16; and PLATE XLIV, FIGS. 10-17. 
Sanguinolites Glaucus, Hall. Prelim. Notice Lamellibranchiata, 2, p. 38. 1870. 
Goniophora glabra, Hall (in error). S. A. Miller. Cat. Amer. Pal. Foss., p. 192. 1877. 
“ “ “ Pal. N. Y., vol. v, pt. 1. Plates and Explanations: PI. 44, figs. 9-17. 1883. 
Shell large, trapezoidal; length once and a half greater than the height; basal 
margin gently curved, sometimes scarcely sinuate anterior to the middle ; 
posterior margin obliquely truncate ; cardinal line nearly straight or slightly 
oblique; anterior end declining from the beaks and abruptly rounded below. 
Yalves moderately convex below, sometimes becoming gibbous in the 
umbonal region. 
