SECTION IV., 1886. RON] Trans. Roy. Soc. CANADA. 
VIII.—Zllustrations of the Fossil Fishes of the Devonian Rocks of Canada. Part I. 
By J. F. WHITEAVES. 
(Read May 27, and revised July 26, 1886.) 
Descriptions of species from the Upper Devonian Rocks at Scaumenac Bay, P.Q. 
PTERICHTHYS (BOTHRIOLEPIS) CANADENSIS, Whiteaves. 
Pterichthys (Bothriolepis) Canadensis, Whiteaves, 1880. American Journal of Science and 
Arts, Third Series, Vol. XX. p. 132. Reprinted in the Canadian 
Naturalist, New Series, Vol. X. p. 23. 
Bothriolepis Canadensis (Whiteaves), Cope, 1885. American Naturalist, Vol. XIX. p. 290, 
with woodcut. 
Cranial and dorsal shields very slightly elevated ; cranial shield moderately arched, 
most prominent immediately behind the superior opening (the orbital opening of Pander), 
where it rises into a low, rounded prominence, or broad and obtuse ridge, which is con- 
tinued with more distinctness and acuteness, but at a slightly lower elevation, along the 
median line of the dorsal shield. 
Outline of the united cranial and dorsal shields broadly elliptical as seen from above, 
their total length as compared with the maximum breadth being about as five to three. 
Cranial shield somewhat semicircular in contour, but much broader than long. 
The shape and relative position of the various plates of which it and the body shield and 
dorsal side of the pectorals are composed, are illustrated by an outline diagram on Plate 
VI (Fig. 1) which represents the whole of the upper surface of the species, as far as 
known, of the natural size and as viewed from above, with the numbers on the plates 
corresponding as far as practicable to those in Pander’s original restoration of “ Pterichthys ” 
under the name Asferolepis! Exclusive of the two side plates (A and B) on each of 
its strongly decurved lateral margins and of those included in the superior or orbital 
opening (Nos. 6 and 6a), the number of plates in the cranial shield appears to be sixteen. 
Of these, the premedian (No. 4), postmedian (No. 8), nuchal (No. 10), prelaterals (No. 5), 
marginals (No. 3), and postmarginals (No. 7), to use Prof. Owen’s terminology, for the sake 
of simplicity, are essentially similar to the corresponding plates in Pander’s well known 
restoration of Pterichthys. 
On the front margin of the cranial shield, however, three narrow and transversely 
elongated plates (Nos. 2 and 2a) take the place of the single “front terminal or rostral ” 

‘In Plate vi. fig. 1 of the monograph entitled “ Ueber die Placodermen des Deyonischen Systems,” published 
at St. Petersburg in 1857, in which the lateral plates of the cranial, dorsal and ventral shieids are numbered on one 
side only. 
