134 J. F. Whiteaves—New Species of Plericthys. 
scribed by Agassiz :* “Les ornemens de cette espéce consistent 
en petits enfoncemens circulaires placés les uns a cété d 
autres et séparés par des carénes qui, par leur juxta-position, 
x 
paraissent hexagonales, 4-peu-prés comme les vitraux ronds des 
ui montaient 4 travers l’écaille pour se ramifier dans 
Vepiderme qui couvrait la plaque.” All the markings so care- 
fully described in the above passage, even to the minute perfo- 
rations through the plate in the center of each pit, can be made 
out with perfect ease in most of the specimens collected by 
Messrs. Ells and Weston. 
The Canadian Ptericthys is so closely allied to the Bothrio- 
lepis ornata that it is by no means certain whether the two are 
specifically distinct or not. Apart from its peculiar sculpture, 
the specific characters of B. ornata are very imperfectly ascer- 
tained, the species having been founded exclusively on a few 
large isolated plates of a placoderm, from the Devonian rocks 
of Russia and Scotland. Until more perfect examples of B. 
* Monographie des Poissons Fossiles du Vieux Gras Rouge, &c., page 99. 
