496 Dr. R. H. Traquair on the 



Trautschold's contribution to the structure of Bothriolepifi, 

 published shortly afterwards (12) , consists largely of corrections 

 of Lahusen's ])aper in matters of detail. He also formulates 

 the differences between the heads of Bothriolepis and Astero- 

 lepis, laying stress on much the same points as Lahusen, but 

 adding that the angular and opercular elements (Pander) 

 found in the latter are wanting in the former genus, though, 

 strangely enough, the angular is represented in the diagram 

 which he gives of the head in Bothriolepis. Noteworthy it is 

 that he mentions having found in one specimen a lid or cover 

 to the " orbit," and accurately fitting it. As regards the arms, 

 of which he had no complete specimens, he ])ointed out certain 

 differences in the arrangement of their constituent plates and 

 considers it doubtful whether the limb was divided into proxi- 

 mal and distal portions, as in Asterolepis. 



The discovery by the officers of the Canadian Geological 

 Survey of numerous well-preserved entire specimens of 

 Bothi-iolepis in the Upper Devonian rocks of Scanmenac Bay 

 enabled ]\Ir. Whiteaves to give a description (13, 14, 15), ac- 

 companied by excellent figures, of anew species of the genus, 

 to which he gave the name oi Ptericlithys {Bothriolepis) cana- 

 densis. These specimens are certainly the finest examples of 

 Asterolepid remains yet discovered, and clearly show all the 

 salient features of Bothriolepis in a manner never before 

 exhibited. Unfortunately Mr. Whiteaves does not seem to 

 have had complete access to the literature of the subject, as 

 he makes no reference to the papers of Egerton and Bey rich 

 on Ptcrichthys or to those of Lahusen and Trautschold on 

 Bothriolepis^ and consequently does not seem to be aware that 

 the identity of Asterolepis, Eichwald and Pander, and Pte- 

 richthySj Agassiz, had ever been questioned, or that very 

 tangible differences between Botliriolepis and Asterolepis had 

 been already pointed out ; for as regards the former he says, 

 " It is still open to question, however, whether the geuus Bo- 

 thriolepis is or is not a valid one, and sufficiently distinct from 

 Ftericlithys" (15, p. 106). 



However, he bases his reference of the Canadian species to 

 Bothriolepis on the sculpture of the plates, pointing out some 

 discrepancies in the plates of the head compared with those in 

 Pander's restoration of '■^Plerichthys''^ (^=. Asterolepis) ] and 

 noticing the absence of a tail, he contents himself with saying 

 ''It seems therefore highly probable that Bothriolepis will 

 prove to be distinct from Pterichthys proper." Even as re- 

 gards the species he seems to be in doubt as to whether or 

 not it is distinct from B. ornatiis of Eichwald. 



But if the generic distinctions between Asterolepis and 



