308 PROCEEDINGS OF THE GEOLOGICAL society. ([Apr. 19, 
richthys with the description and figures given by Agassiz of the 
allied genera, I have been surprised by the great similarity between 
the restoration of the genus Pamphractus* and the dorsal integuments 
of Pterichthys. Waving never seen a specimen of Pamphractus, I 
should not be justified in expressing any positive opinion respecting 
this genus, but I cannot help thinking that it is founded on a speci- 
men showing the true dorsal arrangement of the lorication of Pée- 
richthys. The central plate a, the anterior and middle lateral plates 
6, 6 and ¢, ec, and the posterior plate or plates d, d, are arranged pre- 
cisely as I have endeavoured to show was the case in Péerichthys. 
There appears to be some difference in the form and position of the 
cephalic plates, but it is very possible, owing to the mutilated con- 
dition of these parts in the generality of specimens, that this may 
not prove an insuperable obstacle to the reunion of the two genera. 
The genus Chelyophorus is only known from two or three specimens ; 
these are limpet-shaped plates somewhat similar to the dorsal plate 
of Pterichthys. The scale of Actinolepis, figured at plate 31. fig. 15, 
seems also referable to the same position on the fish, in which case 
this genus should be included im the family of the Cephalaspids. 
Homothorax and Placothoraz are assigned to this family, but I have 
not the means of comparing them with Pterichthys. The genus 
Coccosteus, although widely differmg in many respects from Pfe- — 
richthys, has nevertheless some points of resemblance so striking, 
that I have no doubt future discoveries will tend-to determine the 
homological relations of most of the dermal plates of the two genera. © 
The most important pomt for my argument is fortunately that which 
is best known, namely the occurrence of a central lozenge-shaped 
plate similar in form, in position and structure to that found in Pée- 
richthys. This plate characterizes the ventral region of the fish, and 
thus affords remarkable testimony to the accuracy of the view I have 
taken, in assigning the like position to the homologous plate in Pfe- 
richthys. 
Since the above was written, I have been in correspondence with 
Mr. Miller on this subject, and with his full permission I append to 
this paper the information with which he has kimdly favoured me. 
The accuracy of his observation and the idoneity of his descriptions 
are too well known to require any eulogium from me, or any apology 
for communicating them to the Geological Society. The followmg 
speaks for itself :— 
“My collection of fishes of the Old Red, greatly more extensive 
now than it was in 1840, when | had the pleasure of being intro- 
duced to Agassiz, enables me to reply with very considerable cer- 
tainty to your queries regarding the Pterichthys. It is a somewhat 
curious circumstance, that the naturalist of Neuchatel is better ac- 
quainted with the upper surface of this ichthyolite than he himself 
believes. I much question the existence of his genus Pamphractus ; 
but I have specimens which I think demonstrate that the restoration 
to which he gives that name (see Monograph of the Fishes of the 
Old Red, tab. 6. fig. 2) represents m a manner tolerably adequate, 
* Monographie des Poissons Fossiles du vieux Grés rouge, tab. 6. fig. 2. - 
