﻿2:24 ANTIA.RCHA. 



Head and trunk broad, depressed, the scutes ornamented with 

 tubercles partially or completely fused into a network of ridges ; 

 tail [if present] without dermal armature. Lateral sensory canals 

 on the upper aspect of the head united by two transverse commis- 

 sures arising from a point on the lateral iDlates, the anterior directly 



Fig. 34. 



Head of Bothriolepis canadensis, "Whit. — Dorsal aspect, restored by R. H. Tra- 

 quair. ag, angular ; e.l, extra-lateral (operculum) ; I, lateral ; l.occ, lateral 

 occipital ; m.occ, median occipital ; p, postmedian ; jp.m, premedian. 



crossing the premedian, the posterior arched backwards, its right 

 and left halves meeting in a sharp angulation upon the median 

 occipital ; anterior median dorsal plate overlapping the anterior 

 dorso-lateral and overlapped by the posterior dorso-lateral, the two 

 halves of a commissure arising from the lateral sensory canals on 

 the posterior dorso-lateral plates meeting in an acute angle about 

 the middle of its surface. Pectoral appendages at least as long as 

 the armoured trunk, segmented into a distal and proximal portion, 

 the latter being much larger than the former : marginal scutes of 

 proximal portion meeting mesially, with a minute " anconeal " 

 element only on the dorsal aspect ; marginal and central scutes of 

 distal portion more numerous than in PterichtJiys. 



The form and arrangement of the bones occupying the orbital 

 opening of this genus have been discovered and described in detail 

 by Whiteaves \ The present writer has had the privilege of ex- 

 amining the original specimens of the Canadian species elucidating 

 the points made known, and is thus able to confirm all the deter- 

 minations. The arrangement is very similar to that described above 

 in Pterichthys (p. 210) ; but additional information as to the pre- 

 cise form of the narrow, transversely-elongated plate in front of the 

 pineal element is afforded thus : — " The central portion of the little 

 plate is continued downward at nearly a right angle, as a narrow 



1 Trans. Roy. Soc. Canada, vol. iv. sect. iv. (1867), p. 102 ; pi. vi. 



