OF THE SKULL IN SHARKS AND SKATES. 231 
ostean fishes; but in the Kel (Anguilla acutirostris) and its congeners there is a less 
degree of specialization of the Raiine type of face. 
In small, white young of that species, 23 inches in length (the gift of Mr. F. Buck- 
land; see ‘ Nature,’ June 22, 1871, pp. 146-148), I find the following modifications of 
the Teleostean face. 
The hyomandibular has a most extensive otic region, the front and hinder head 
being far apart, and under the latter the opercular knob. This transverse top grows 
downwards, as an arcuate rod, with its convexity behind. 
It is ossified by the hyomandibular centre down to the bent part; then there is a 
large tract of cartilage, which has its pointed forward end capped by a symplectic bony 
sheath, which passes inside the quadrate in front of it. 
On the back of the middle of the synchondrosial tract there is an interhyal nucleus 
of cartilage, from which a ligament grows; and to this ligament the hyoid cornu is 
suspended. This cornu does not separate off into a hypohyal below; and the epi- 
and ceratohyals completely ossify the rod, largely overlapping each other. 
Below its front condyle the hyomandibular sends forwards and downwards two strong 
sharp spines of periosteal bone ; and these embrace the ascending but lowered head of 
of the mandibular suspensorium, which is a shortish straight rod, unossified above and 
below. 
Its ossification is a cylindrical, ectosteal quadrate; and the apex receives no meta- 
pterygoid bony centre. 
As in the Urodeles, there are a bony and a cartilaginous pterygoid; the former is a 
delicate f-shaped style, pedate behind, to run up the front face of the suspensorium. 
The cartilaginous pterygoid (r. pg, rudiment of pterygoid) is a triangular process, 
growing from the front of the quadrate bar below, exactly as in the larva of every known 
kind of Caducibranchiate Urodele, as well as in certain Perennibranchiates ; it is also the 
arrested homologue of the part which, in the Salmon, coalesces with the ethmopalatine, 
and also of the extended limb of the ‘upper jaw” of the Selachian. 
The ethmopalatine is suppressed in the Eel, and its skull is as simple as that of a 
Snake or of the Proteus. 
But a skull whose structure has long puzzled me, namely that of the Siluroid Clarias 
capensis, comes in as the most demonstrative proof of the existence of a preoral post- 
nasal visceral arch. 
As in the Eel and its congeners, the hyomandibular of Clarias has an extensive otic 
region ; and, as in the Eel, the fore part of that bone develops an extraordinary amount 
of periosteal bone in front, which aborts, or coalesces with the metapterygoid. 
The whole pterygo-quadrate arcade is a broad, flat, almost transverse plate, not ascend- 
ing behind into an otic process, but being angular behind and above the quadrate con- 
dyle, and strongly wedged in between the foregrowths of the hyomandibular and the 
separate symplectic bone. 
2K 2 
