THE DEVONIAN FOSSILS OF CANADA WEST. 269 
Locality and Formation.—At most localities of the Devonian rocks 
in the County of Haldimand, Oriskany Sandstone, and Corniferous 
Limestone. 
Collectors.—K. DeCew. J. DeCew. E. Billings. 
Genus PENTAMERUS.—(Sowerby.) 
Generic Description.—Shell, globular or sub-globular, the ventral 
valve the larger, and usually with a prominent, greatly developed 
umbo. A strong mesial septum in the interior of the ventral valve, 
supporting a triangular chamber beneath the beak. “In the interior 
of the smaller (or dorsal valve) there are two distinct longitudinal 
septa, of variable dimensions ; (between which a small median ridge 
is occasionaly found), to these the socket walls converge and join, 
forming two more or less developed and inclined plates, to the produced 
extremities of which were affixed the spiral cirrated arms.’’ (David- 
son, Introduction, p. 98.) 
This genus ranges from the base of the Trenton Limestone up to 
the carboniferous rocks. 
7 
PENTAMERUS ARaTus.—(Conrad.) 
Arrypa ARATA and Atrrypa ocrocostata.—(Conrad.) Annual 
Report on the Paleontology of New York, p. 55, 1841. 
PENTAMERUS ARATUS.—(Hall.) Tenth Annual Report of the Re- 
gents of the University of the State of New York, p. 120, 1857. 
Fig. 94, 
Fig. 93. 
Fig. 938.—Pentamerus aratus, Dorsal view of a very large specimen. 
Fig. 94.—Side view of the sau.e specimen. 
Vor, Vi. r 
