[MATTHEW] ORDOVICIAN SYSTEM ON THE ATLANTIC COAST 257 
that of an Acrothele ; the concentric ridges are of unequal size, and there 
are occasional more distinctly marked growth-lines, 
Size—Length of the dorsal valve, 13 mm. ; width about the same ; 
the ventral valve is about 15 mm. longer. 
Locality —Same as the preceding. Found in a sandy limestone by 
Messrs. Weston and Robert. 
This species is very little larger than the preceding, but is distin- 
guished by its radular ornamentation and thicker valves; also by its 
acuminate upturned beak, its tumid dorsal valve, and by the position of 
the central muscular scars of this valve ; these scars are in the posterior 
half of the valve, but in Z. Selwyni about the middle of the valve. 
Mr. J. F. Whiteaves has very kindly loaned me for comparison 
with the Lingulellas of the Ordovician of the Atlantic coast, examples of. 
a Linguloid shell from Beverly, Ontario. Some of these shells show the 
interior surface of the valve, and are described and figured to show the 
distinctness between the genera Lingulella and Lingulepis in the position 
of the muscular imprints, etc. 
LINGULEPIS, Hall. 
LINGULEPIS ACUMINATA, Conrad, PI. IT. figs. 5a and b. 
Lingula acuminata was originally described by T. A. Conrad from 
specimens found in boulders from the calciferous sand rock ! of the State 
of New York. The specimens, however, are very much smaller than the 
Canadian shell I am about to describe, and differ considerably in form ; 
still Mr. Walcott appears to recognize Conrad’s species as identical with 
the species from the Upper Cambrian near Saratoga, described by him, 
some examples of which are represented as attaining the size of the 
Canadian form ; and further he compares the Saratoga form with LZ. 
pinnæformis, which evidently is congeneric with the Canadian form. The 
western species, however, is more prolonged at the beak than thé ex- 
amples of L. attenuata tigured by Dr. Hall, or than those of the Canadian 
form. 
It is chiefly the internal characters of the Canadian shell that will be 
described : 
The ventral valve appears to have no area, but finishes with a rim 
similar to that of other parts of the shell. Near the umbo there is a 
narrow extension of the visceral callus upon which is a small scar of the 
cardinal muscle. Jixtending forward on each side of the narrow part of 
the callus are bands along which the lateral muscles travelled during the 


1 Paleontology of New York, vol. i., p. 9, fig. at bottom of the page. 
Sec. IV., 1895. 17. 
