OF THE SKULL IN THE URODELOUS AMPHIBIA. 
569 
the influence of the chondrocranium, which, itself also, has acquired the power of con- 
verting considerable tracts of its own substance into a hardish kind of bone. 
This skull, comparable to that of an Eel or a Snake, has its lateral halves only con- 
jugated slightly before and behind ; thus the main part is devoid of any intrinsic floor ; 
the basal fontanelle is very large indeed. 
If the hind pair of sense-capsules (pro., ep.) were not fused with the skxill proper, it 
would indeed be a feeble framework — just a pair of feebly out-bent bars slightly 
soldered together at either end, and having the facial rods very loosely swung to each 
side-piece, the main pair, only, confluent at one small point (pd.)*. 
The superoccipital ring was imperfect in its cartilaginous condition (Plate 28. fig. 4, 
s.o .) ; but the bony substance has formed a very narrow keystone. Below, the shrunk 
and retired notochord lies on a narrow ossified bridge of cartilage, and thus the ring is 
complete. The condyles (oc.c.) are large, non-pedunculate, and look inwards ; the large 
notch between them betokens the presence of an odontoid process on the first vertebra, 
not the homologue of the mammalian spike, but an aborted intercalary vertebra. The 
occipital floor is inseparable behind from the parasphenoid, which it thickens postero- 
laterally, the bony matter running thence into the base of the ear-capsules on their 
inner side. By the analogy of Menobranchus I should suppose that the epiotics were 
at first distinct ; they are not now. The ear-capsules are like egg-shaped fruits, and are 
very large, relatively ; unlike those of most of their order, they show scarcely any impress 
of the arched tubes and swollen bags within. The whole capsule, like the Diatomaceous 
Isthmia, is composed of two hard cases united by a zonular intermedium ; this is com- 
posed of unchanged cartilage; they are the prootic and epiotic bones (pro., ep.) (the 
latter includes the opisthotic), and their appearance is as if they were ready to dehisce 
transversely, like the pyxidium of the Pimpernel (Anagallis). These thin divisions 
are subequal, the prootic being the larger. Infero-laterally there is a long fenestra 
ovalis, and its adapted stapes (s£.) is a long oval shell of bone, a little soft at its narrower 
front end. The epiotic is roughened with bony granules where it projects backwards as 
the hindermost part of the skull ; in front the capsule is lowest, and the granules mark 
the uplifted epiotic apicular cap. 
Instead of the prootic applying a long wall-plate to the side of the skull, as in Siredon , 
it sends forwards a most minute cup, and into this the end of the trabecula fits. That 
was not the end, but the elbow of the bar, whose notochordal outspread portion has 
been absorbed. As in the Snake, the trabeculae persist as filiform cartilages ; they are 
* Professor Huxley’s paper on the kindred form, Menobranchus lateralis (P. Z. S., March 17, 1874) will be 
incessantly referred to in this description ; whilst writing it I have dissected the skull of one 10 J inches long, 
and probably somewhat younger than his specimen. In mine there is a superoccipital band of an inch 
across, and an ossified bridge of cartilage below the notochord, just in front of the foramen magnum. The huge 
epiotics were thoroughly distinct, which is a remarkable character, as they are generally only a tract of the 
exoccipital. The absence of bony matter in the sphenethmoid region is very remarkable ; the want of cartilage, 
across, behind the pituitary body, is due to absorption of the flat parachordal apices, or hind end of the tra- 
beculae ; it is not a primitive condition. 
MDCCCLXXVII. 4 L 
