THE DEVONIAN FOSSILS OF CANADA WEST. 275 
Ruynconewsa (7) Laura.—wh. Sp. 
Fig. 26. Fig. 28. 
Fig. 27. Rhynconella Lawra.—Vorsal aspect. Fie. 27. Phe same; ventral aspect. 
A 
Fig. 28. Side view. 
Description.—Ovate; greatest width at about one-third of the 
length from the front; sides gently arched from the beak to the line 
of the greatest width; front angles narrowly rounded; both valves 
convex, sometimes rather gibbous. Ventral valve most elevated a little 
above the middle; umbo rather obtusely rounded, not very prominent; 
beak short, obtuse, closely incurved, in contact with the umbo of dor- 
sal valve; a broad mesial sinus which usually becomes obsolete at one 
half the length, but can be sometimes traced nearly to the beak. 
Dorsal valve with a mesial fold, corresponding with the sinus of the 
ventral valve in length. 
Surface with about seventeen rather large rounded obscure slightly 
elevated ribs, of which there are four or five in the mesial sinus, and 
five or six on the mesial fold. A few squamose rings of growth. 
Length of large specimen twelve lines; width eleven lines. Another 
individual from the same locality is nine lines long and ten wide. 
Locality and formation.—Bosanquet. Hamilton Shales. 
Collectors.—T. Richardson, A. Murray. 
Genus Avtuyris.—McCoy. 
There is much difference of opinion as to the propriety of retaining 
this generic name. It implies that the shells have no foramen in the 
ventral valve, and yet many species are placed in the genus which have 
the beak distinctly perforated. Some paleontologists are, therefore, 
in favor of using De Orbigny’s appellation Spirigera, instead of 
Athyris. Nearly all of the Silurian species, and some of those from 
the Devonian rocks, have the beak so strongly incurved, that no 
foramen can be seen. For such, at least, the name Athyris does not 
appear to be very inappropriate. Mr. Davidson still retains it, not 
