Dr, Rk. H. Traquair—Old Red Sandstone Fishes. 513 
a series of vertical tubes, but without the cross branches which in 
the dendrodont arrangement form an intricate network of vessels. 
Zittel, in his Handbuch, refuses to accept these families as distinct, 
but, adopting as a “family” the Cyclodipteride of Liitken, divides 
the genera into— 
“ (a) Unvollkommen bekannte Formen mit dendrodonten Zahnbau 
(Dendrodus, Cricodus, ? Colonodus, ? Sigmodus). 
(6) Formen mit langgestielten Brustflossen (Holoptychiide, 
Traquair). 
(c) Formen mit kurzgestielten Brustflossen (Rhizodontide, 
Traquair).” 
Here it may be observed— 
First, that there is no reason for separating Dendrodus from the 
Holoptychii, the latter being in fact ‘‘dendrodont.” 
Second, that Cricodus (= Polyplocodus, Pander), which he includes 
in his first category, is certainly not dendrodont, but Rhizodont in its 
tooth structure. 
Third, that to include the forms with “lang-” and “kurz- 
gestielten Brustflossen” in one “family” is contrary to current 
ideas of zoologists as to the limits of such a group, indeed one might 
as well go back to Agassiz’s plan of having ‘“ homocercal” and 
“‘heterocercal divisions” of such a so-called ‘“ family ” as in his now 
discarded “ Lepidoidei ” and “ Sauroidei.” 
The species of Holoptychius are extremely difficult to define, and 
having only a few days ago received an interesting paper from M. 
Lohest, of Liége, on this subject, I shall defer their consideration 
for the present; meanwhile 1 must express my opinion that the 
scattered teeth and fragments of jaws known as Dendrodus and 
Lamnodus belong to fishes at present known to us by their scales as 
species of Holoptychius and Glyptolepis. 
The large head figured by Prof. Huxley as that of Glyptopomus 
minor, Ag., certainly belongs to Holoptychius, probably ZZ. Flemingii, 
which seems sometimes to have attained a large size. The genus 
Platygnathus, Ag., also does not exist, as Pl. Jamesoni, Ag.—concerning 
which Huxley wrote that it cannot be doubted that it “is very 
closely allied to Holoptychius”’—is clearly the tail end of a Holopty- 
chius turned upside down, the lower aspect of the caudal being 
mistaken for an enormous dorsal, and the second dorsal for an anal ; 
while the mandible from Orkney figured by Agassiz as Platygnathus 
paucidens, is with equal certainty referable to the same large species 
of Glyptolepis whose sculptured scales and dendrodont teeth were 
attributed by Hugh Miller to his “Asterolepis of Stromness”’ 
(Homosteus). This magnificent Glyptolepis, of which the Edinburgh 
Museum now possesses several entire specimens from Thurso, must 
therefore stand as G. paucidens, Ag. sp.; and as synonyms of 
G. leptopterus, Ag., 1 must include Z/oloptychius Sedgwicki, McCoy, 
and Glyptolepis elegans, Ag. We shall presently see that Glyptolepis 
microlepidotus, Ag., is not referable to Glyptolepis at all, but belongs 
to a different family. 
DECADE III.—VOL. V.—NO. XI. 33 
