278 THE DEVONIAN FOSSILS OF CANADA WEST. 
The specimens that have come under my observation have in 
general the same amount of convexity, the depth of both valves 
being in all about two-thirds the greatest width. 
The surface is nearly smooth; a few obscure concentric undula- 
tions of growth and fine striz,—of the latter, twelve to fifteen in the 
width of one line are visible on well preserved shells. There are 
also faint indications of longitudinal radiating lines. A fragment 
of one individual of this species exhibits a surface uniformly marked 
with fine rounded concentric undulations (not striz), of which there 
are four of five in the width of one line. 
This species has, to some extent, the aspect of a Pentamerus ; 
but its internal structure, as exhibited in the numerous broken 
specimens that I have examined, shews it to be congeneric with 
A. Clara. It differs from that species in having the mesial fold and 
sinus extending the whole length of the shell, and the beak of the 
ventral valve not touching the umbo of the dorsal valve. 
Locality and formation.—St. Mary’s, Township of Blanshard. 
Corniferous. 
Collectors.—Mr. W. G. Tomkins, C.E., St. Mary’s, C.W.; A. 
Murray; J. Richardson. 
Aruyris (?) Sciruta.—(Hall.) 
Arrypa sciruta.—Hall. Geology of the Fourth District of the 
State of New York, p. 171, fig. 1. 
Fig. 35. Fig. 36. 
Figs. 35 to 38.—Different views of a small and large specimen of A. scituila. 
’. TheSabove figures represent different views of two specimens of a 
species which appears to me to be identical with that figured in the 
work fabove cited. It varies greatly in size. The length of the 
