STHUCTURE OF CERTAIN PALEOZOIC DIPNOI. 
195 
perfectly preserved heads, and our figure is therefore less complete in that 
part than the corresponding figures for Sagenodus (fig. 17, p. 182). Miall 
had apparently seen examples, though still more imperfect ones, of the same 
bone (1880, fig. 12), and he evidently suspected that it belonged to the 
shoulder-girdle of Ctenodus proper, for he labels it " Ctenodus cristaius or 
tuhercidatus'i Coracoid." 
We have found one or two bones which may prove to be post-temporals 
of Ctenodus, but have not been able yet to identify them with any approach 
to certainty. 
Fia. 26. 
Ctenodus cristatus. Pterygoids with their teeth, in natural articulation 
■with the parasphenoid. Quadrate rami shown flattened into the same 
plane as the parasphenoid. x y. 
? lie Species of Ctenodus. 
Dr. Smith Woodward was probably well advised in reducing the specific 
names tubercidatus, ovatus, etc., to the position of synonyms of C. cristatus. 
The tooth-plates of Ctenodus, on which all the specific names have been 
founded, are if anything more variable even than those of Sagenodus. They 
are, in fact, likely to be so, since they represent a departure from the standard 
Dipnoan type of dentition as established in Dipterus and carried on in 
Sagenodus and Ceratodus. A perfectly distinct species, however, is the 
