106 WHITEAVES ON FOSSIL FISHES FROM 
and Heterostius of Asmuss—the example of British palæontologists will be followed, in 
retaining the name Prerichthys.” ' 
In 1857 Dr. Pander published an able and elaborate illustrated monograph on the 
Placoderms, to which reference has already been made, and his restorations of the dorsal 
and ventral aspects of “ Pterichthys,” as it is now generally called, have since been copied 
in several manuals of geology and paleontology. In this monograph Dr. Pander main- 
tains that Prerichthys (Agassiz) and Bothriolepis (Eichwald) are both synonyms of Asterolepis 
(Eichwald). As far as the names Asferolepis and Pterichthys are concerned, the latter has 
been very generally adopted by paleontologists, for the reasons already stated in Prof. 
Owen's words. It is still open to question, however, whether the genus Bothriolepis 
is or is not a valid one, and sufficiently distinct from Plerichthys. If it is a valid genus, 
which there are good reasons for supposing it to be, then it has not yet been properly 
defined. The Canadian species, now under consideration, certainly has the pitted 
sculpture of Bothriolepis (as pointed out by the writer in 1880), and, if Pander’s restora- 
tion of Pterichthys be correct, then Bothriolepis would seem to differ from it in several 
particulars, but more especially in the structure of the mouth organs. Thus, Pander 
represents Pterichthys as having a lower jaw, beneath which there are maxillary plates 
which are separated from the cranial shield by a deep cleft. No indications of a true 
lower jaw have yet been detected in the Canadian species, and the only plates (A and B) 
in it which might be supposed to represent the inferior maxillæ of Pterichthys are not 
separated from the cranial shield by a deep cleft, but, on the contrary, are firmly articu- 
lated to it. Moreover, the two small oval plates (No. 6 a) on each side of the median 
plate (No. 6) in the orbital cavity (whatever may have been their function) and the 
singularly deflected little plate (No. 6 6) between the median (No. 6) and the premedian 
(No. 4), in the Canadian species, are not represented at all in any of Pander’s restorations 
of Pterichthys, though they may not have been preserved in any of the specimens to 
which he had access. 
Again, the tails of Scotch examples of Pterichthys are distinctly stated to be covered 
with small ganoid scales; but not a trace of any such scales has yet been discovered in 
the many specimens that have been collected of the present species. Prof. Huxley has 
suggested that Pterichthys may have been a teleostean fish allied to the Siluroids; but if 
that were the case, we should expect to find some remains of its vertebral column or of 
other parts of its endoskeleton. 
It seems, therefore, highly probable that Bothriolepis will prove to be distinct from 
Plerichthys proper, and, if so, then the Canadian species will have to be referred to the 
former of these two genera. 
The Pterichthys (or Bothriolepis) of Scaumenac Bay is so closely allied to the Bothrio- 
lepis ornata of Eichwald, 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 ascertained, the species having been founded exclusively on a few large 
isolated plates which have been collected from the Devonian rocks of Russia and 
Scotland. Until more perfect examples of B. ornata shall have been described and figured, 
it will be impossible to institute an accurate comparison between its specific characters 


* Paleontology, 2nd ed., Edinburgh, 1861, p. 140. 
