‘Cope.] 584. [March 7, 
open above. The neurapophyses it is true unite, but at a distance above 
the neural cord, and as attenuated rods. Third, ‘‘There isno vomer de- 
veloped, but a triangular cartilaginous element pendent from the cranial 
rostrum affords attachment for the palatine (read maxillary) element 
anteriorly,’”’ etc. This element probably exists in the Colocephali and 
similarly takes the place of the vomer, only differing in being ossified. 
I have been accustomed to regard it as the homologue of the bone called 
ethmoid in fishes. 
The character which distinguishes the Colocephali from the Enchely- 
cephali, now that their maxillary and palatine structure are shown to be 
essentially the same, is found in the hyoid apparatus. In the Enchely- 
cephali, the structure is as in ordinary fishes ; there is a glossohyal, and 
there are basihyals, and axial branchihyals, and superior pharyngeals. In 
the Colocephali all these elements are wanting, excepting the fourth supe- 
rior pharyngeal, which has the form of an antero-posteriorly placed den- 
tigerous jaw, which opposes the lateral branchihyal of the fifth arch or, 
as it is generally called, the inferior pharyngeal. It is evident that the 
Eurypharyngide are more similar to the Colocephali than to any other 
order in this respect also, but the description of these parts is not yet suffi- 
ciently detailed to enable me to determine what difference there may be 
in this respect, if any. The mobility of the quadrate bone on the hyo- 
mandibular cannot be regarded as of great systematic significance, although 
it is doubtless important in the economy of the fish. 
It is then evident that the Eurypharyngidee belong very near to, if not 
within, the order QVolocephali. Towards the end of their description, 
Messrs. Gill and Ryder (p. 270), recognize this relationship, but deny that 
it indicates that this family is ‘‘from the same primitive stock as the 
Mureenids.’”’ I incline to the belief that it is the ultimate result of the 
line of development of which the Anguillide form one of the first terms, 
and the Murenide a later and more specialized one. 
It is therefore clear that the point of relationship of the Ichthyotomi to 
the true fishes is not to be found in the Eurypharyngide or the Colo- 
cephali. 
In the following point Didymodus resembles Polypterus. The fossa 
above described as on each side of the basioccipital, is found in Polypterus. 
There it serves as a place of insertion of a strong ligament on each side, 
which is attached externally to the epiclavicle, and serves to hold the 
scapular arch in its place. A similar structure exists in the Siluirde, 
where the ligaments are ossified. It suggests for Didymodus a scapular 
arch suspended more anteriorly than in sharks, possibly even to the skull. 
The genealogy of the fishes will then be as follows, first, however, it 
is to be understood that in asserting the derivations of one group from 
another, I mean that in accordance with the rule which I have termed 
“the doctrine of the unspecialized,’’ the later type in each case is the 
descendant of the primitive and not the later sub-form of its predecessor. 
In this way is to be explained the apparent anomaly of regarding the 
