DEVELOPMENT OF THE SKULL IN THE URODELES. 211 
as that of the Newt, we shall find that only those scutes have been retained in the latter 
that are always the most constant in the Vertebrata above the Ichthyopsida, altogether. 
This fact is disclosed at once when we see that most of the surface-plates in the 
Newt’s skull can, in a moment, be named by the same names that their representatives 
have received in the highest Birds and in the highest Mammals. 
These are they that were at first brought, in the Ganoid Fishes, under the influence 
of the brain in its regions, of the sense-capsules right and left of the brain, and 
of the apparatus and armature of the mouth. 
We see, also, that the Newt has dropped (suppressed), even in its larval state, 
the special scutes that protect and amplify the branchial apparatus in the Ganoid 
and Osseous Fishes; these are here suppressed at once and for ever (with the slight 
exception of a few parts that are retained for new functions) in every ascending branch 
of the Great Vertebrate Life-tree. 
A list of the superficial bones to be found in the Newt’s skull will seem to be rather 
that of some growing Bird or Mammal. They are as follows :— 
1, frontals; 2, parietals; 3, nasals; 4, squamosals; 5, premaxillary; 6, septo- 
maxillaries (found in certain Birds); 7, maxillaries; 8, vomers; 9, palatines; 10, 
pterygoids; 11, parasphenoids (existing in three pieces, early united, in the Bird, and 
as two (hinder) ossicles—the “cornua sphenoidalia” in certain Mammals); 12 
dentaries (or mandibular rami); 13, splenials (constant in the Bird class). 
In the endocranium the low, and perhaps archaic-selachian, origin of these forms 
is indicated by the generalized nature of the truly bony tracts. In the Selachians we 
only see the crowding of the superficial calcifications of the cartilaginous structure in 
certain parts; here, in the Newt, calcification rapidly passes into ossification, but the 
“centres” run riot over two or three morphological territories at once, and do not keep 
to proper imternewral spaces. 
Yet, even thus, the nomenclature is not difficult; the terms merely have to be coni- 
pound, like the parts they stand for; the “sphenethmoid” is, for example, a bone 
answering to the sphenoid and ethmoid of human anatomy. 
I have compared Triton with Lepidosteus for the sake of illustration, and not as 
seeking to derive the Newt from that or any such Ganoid Fish; I am not speaking of 
actual genesis, but of the general order of the specialization of parts. 
On the other hand, I am inclined to think that the Urodeles came up from types 
that specialized their dermal scutes very sparingly, like the Lipidosiren ; whose ancestors 
(probably) had simple chondrocrania that had subjected the dermal armature to no 
> 
special modification. 
Within the limits of this small contribution I have been able to show how remark- 
ably the stages of a small high “Caducibranch” correspond with the permanent 
condition of darge and low types. 
But if to this paper we add Dr. Wiedersheim’s invaluable memoirs, and the other 
VOL. X1—PaRT VI. No. 6.—January, 1882. 2K 
