and Structure of the Proteus Anguinus . 85 
themselves are so thin that the entire mass of brain is some- 
times visible through them. The temporal bones send pro- 
cesses forward, which articulate with the lower jaw. The two 
frontal bones are long, and lie nearly in the same plane with 
the irfra maxillary ; but the cranium is a little depressed, in 
that part formed by the parietal bones. Both jaws are fur- 
nished with teeth, which are arranged in a beautifully sym- 
metrical order along their respective borders. These teeth 
have a conical figure. In the upper jaw, their number is 
about 60; in the lower jaw there are 70, disposed in two 
rows parallel to one another. The lower jaw is horizontal, 
and has no ascending process where it articulates with the 
temporal bone. 
The os liyoides in the proteus is short : its anterior branches 
extend backwards and outwards, and then bending upwards, 
proceed to be attached by a large tendon to the sides of the 
cranium, behind the articulation of the lower jaw *. The small 
arches which sustain the gills are three on each side; the 
first, or exterior one, is the largest ; it is connected anteriorly 
with the posterior extremity of the os hyoides, by the inter- 
medium of a little bone : the second, or middle arch, is also 
furnished with an intermediate bone, which is attached to the 
intermediate bone of the first arch : the third, or interior 
arch, has no intermediate bone, but is connected directly with 
the second by means of a cartilage. The relative size and 
position of all these parts may be seen in Plate VI. Fig. 1, where 
the bones of the head, viewed from below, are represented 
eight times greater than natural. 
From the occiput to the extreme point of the tail there 
are 59 vertebrae, all of which, except the last, have an osseous 
structure. Of these, 29 belong to the neck and back, 3 to 
the sacrum, and 27 to the tail. The first vertebra, or atlas. 
* In the Plates, the animal is exhihited in a reversed position, but in the ana- 
tomical descriptions, is supposed to be placed on his four feet ; hence the terms 
anterior, or forward, look towards the head ; posterior, or backward, towards the 
tail ; superior, or upward, to the back ; and inferior, or downward, towards the 
belly of the animal. The terms interior and exterior are used to denote relative 
nearness to, or distance, from the median line ; and those of internal and external 
refer simply to the inside or outside of the animal. 
