578 
ME. AV. K. PAEKER ON THE STRUCTURE AND DEVELOPMENT 
The suboval, convexo-concave condyles ( oc.c .) look mainly downwards and a little 
inwards ; they have a very short neck. 
More of the ossified endoskeleton is hidden by the single parasphenoid below than 
by the paired parietals above. 
One large and some lesser teeth of a suture can be seen between the prootic {pro.) 
and the epiotic overgrowth of the exoccipitals. I say overgrowth , because in these 
Caducibranchs I find no separate epiotic or opisthotic, both these regions gathering 
bone from the edge of the exoccipital. 
The prootic ossification {pro.) is very large; it occupies all but the hinder fourth of 
the capsule ; and it is remarkable that the only part unossified by it (except that which 
belongs to the exoccipital) is on its anterior face (figs. 4 & 5), from the front of the 
anterior ampulla to the facet for the pedicle. The stapes {st.) is a little bony lozenge. 
The soft tract is due to an ensheathing of the capsule by the basal plate ; thus the 
pedicle articulates with that, and not with the proper capsule. 
The chondrocranium is like a little boat with the bottom out, but replaced by an 
extraneous plank, the parasphenoid {pa.s .). The sides of this boat-shaped skull are 
hardened by ossification, the cartilage ultimately yielding to true bone ; this bony tract 
reaches from the prootic and foramen ovale to near the internal nostril {i.n.) ; it is 
deficient above, from the optic foramen (2) to the ear-capsule. 
I know of no Urodele in which an overlying “ supraethmoidal” bone conjugates into 
one “ girdle-bone ” these two lateral tracts or “ sphenethmoids,” although Siren has 
two such superficial plates, and the Menopome one. 
The rest of the chondrocranium is cartilaginous; it consists in the Urodele of the 
nasal roofs, coalescent with the internasal plate, or the remainder of the trabecular 
cornua in front of the unossified wall of the skull or of the sphenoethmoidal tracts. 
Behind the internal nares {i.n.) there is a thick lip of cartilage, the antorbital or 
ethmo-palatine {e.pa.) ; it is confluent in the adult with the nasal capsule. In the 
larva (figs. 1 & 2) it had not appeared. 
Part of the nasal roof can be seen in the outer nostril {e.n.)*c Up to the ethmoidal 
region the skull is very bony ; in some, as Salamandra maculosa , there is a band of 
cartilage, across the floor, some distance in front of the parachordal region, which is 
ossified by the prootics ; in Triton cristatus this band vanishes in the adult. 
In Osseous Fishes this part is large, and is ossified by the prootic, forming the prootic 
bridge (“ Salmon’s Skull,” plates 7 & 8) ; it is formed by the trabeculae ; and thus 
there is in many types a perfectly clear distinction between those bars and the investing 
mass throughout life. 
The roof of the skull in the adult Seironota is a strong piece of masonry. 
The parietals (figs. 4 & 6,p.) are about the size of the frontals (/.); they are 
* In a future communication I shall show the condition of the chondrocranium in the adult Triton and 
Salamander , after the outer bones have been removed. 
