210 PROF. W. K. PARKER ON THE STRUCTURE AND 
the suspensorium; whilst one type, viz. Ranodon sibiricus (op. cit. pl. v. figs. 68-70), 
finishes its suborbital band by confluence of the pterygoid cartilage with the ethmo- 
palatine, a secondary condition answering to that which is primary in the “ Anura.” 
But the specialization of the Newt, as a typical metamorphosed Urodele, is quite 
as noticeable for what is left out as for what is developed: the presence of certain 
elements in other types is, in them, indicative of a somewhat generalized constitution. 
The finished skull of the Newt is similar to and yet very different from that of the 
Common Frog; it is much more ossified, although smaller, has no cavum tympani, 
no columella, an open jugal space, but with the quadrate region well ossified intrin- 
sically. 
It keeps the main roof-bones distinct, has no postorbital process to the squamosal, 
whilst, after giving off a pterygoid bone, the palatine coalesces with the vomer, and, 
instead of applying itself to the ethmopalatine cartilage—its own endoskeletal counter- 
part—whilst that is transversely placed, the bone runs backwards at a right angle to it, 
reaching nearly to the auditory region. 
Hence we see that under the outward likeness of these two small Amphibian skulls 
there lie hidden a number of the most remarkable contrasts; these contrasts, however, 
are not greater than those which exist in the primordial chondrocranium of the larve 
of these types. 
Passing from the “ Elasmobranchs,” in which the placoid dermostoses are not brought 
under the influence of the slightly calcified chondroskeleton, to the “ Ganoids,” in 
which the larger and more perfect dermal scutes are subjected, in the head and 
shoulders, to the organic attraction of the parts beneath, we perceive a great difference. 
The scutes of the fore part of the animal are manifestly the “serial homologues” of 
those of the hind part; but in size, number, and form they are greatly changed ; some 
have been selected for one purpose, and some for another. 
The principal regions of the brain, the sense-capsules, the apparatus of the mouth, the 
hyobranchial arches—all these draw unto themselves such scutes as they need for pro- 
tection, and for the finishing of the mechanism of the mobile arches. 
Still many of the scutes are simply a repetition of those on the body, and only a 
certain number stand out as distinguished from the rest by their size, their form, and 
their relation to the deeper structures. 
These are seized upon by the morphologist as representatives of the superficial 
bones that, in higher types, have been selected for various functions, that have been 
completely transformed in accordance with their new relations, and that in those 
higher forms lose their surface-layers and exist only as subcutaneous bony plates that 
often combine with the deeper skeletal structures to form the highly compounded 
skull. 
If we make a stride, at once, from such a skull as that of Lepidosteus to such a skull 
