THE DEVONIAN FOSSILS OF CANADA WEST. 263. 
Fig. 80. Fig. 81, 
Fig. 80.—CyrT1A HAMILTONENSIS.—Hall. Ventral view. 
Fig. 81.—Side view, 
Fig. 82.—Dorsal view. (The perforation not shewn near the beak in the figure, but exists 
in the specimen.) 
gular at the extremities; dorsal valve depressed, nearly flat; beak 
searcely elevated above the hinge-line ; mesial fold small, bounded on 
each side by deeper and wider grooves than those between the plica- 
tions, with sometimes a faint, narrow, longitudinal depression in the 
middle ; ventral valve very convex, most prominent near the beak, 
which is very variable in elevation, and either straight or a little 
arched from the hinge, sometimes twisted on one side ; sinus distinct, 
rounded or angular; area variable, triangular, generally high, often 
wider than high, arcuate or plane, finely striate in both ways, the 
vertical strize scarcely visible ; foramen very narrow, usually perforate 
above by an ovate aperture, and has at its base a small transverse 
arcuate slit. Surface ornamented by six to eight simple rounded 
plications on each side of the mesial fold and sinus, and marked by 
very fine concentric lines of growth. Under a good lens, minute 
granules may be seen on all parts of the exterior except the area and 
deltidium : interior minutely punctate.”—(Hall. Tenth Regents’ 
Report, above cited.) 
Our specimens agree so exactly with the above description, that 
there can be no doubt of the identity of the species. 
Locality and formation.—Townships of Bosanquet and Plympton, 
Hamilton shales. 
Collectors.—A. Murray, J. Richardson, E: Billings. 
CyRTIA ROSTRATA.—(Hall.) 
A species of Cyrtia occurs in the Corniferous Limestone, only 
differmg from C. Hamiltonensis in having the ribs larger and the 
surface marked with concentric imbricating lamelle, instead of fine 
strie. The only perfect specimen I have seen has five ribs on each | 
side of the mesial fold and sinus. It is referred to C. rostrata pro- 
visionally. 
Locality and formation.—Lot 45, Con. 1, Cayuga. 
Collector.—J. De Cew. 
