DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 179 
the parietal (p.), shows the foramen for the ophthalmic nerve (V'.) on its lower 
margin ; its orbital plate leaves much of the endocranium (0.s.) naked; it shows no 
signs of distinctness from the roof-plate of the bone, such as is seen in the Hedgehog. 
The parietal is a fine shell of bone, and is the largest in the skull. The frontal and 
parietal clamp each other mutually in the postorbital region, but the latter imbricates 
itself on the frontal in the coronoid region ; from the top of that suture to the top of 
the lambdoidal, the convex dorsal outline of the bone forms a large and accurate are. 
The compound superficial mandible (d.) is almost perfect, but the coronoid, 
condyloid, and angular processes (c.p., cd.p., ag.p.) are still cartilaginous ; they are 
rounded and sub-equal. 
In the lower view (Plate 26, fig. 2) the surface is only invested with superficial 
bones in the narrow palatine region ; the occipital, and most of the sphenoidal, regions 
are left bare. 
Each premaxillary, carrying three teeth, is well developed, but the palatine 
processes (p.px.) are largely hidden by those of the maxillaries (i. ; see fig. 5); the 
antero-lateral vomers, also, are not seen, they have a very temporary and doubtful 
existence independent of these processes of the premaxillaries. The vomer (v.), also, 
is only partly seen, but is really very large and typical (fig. 5, v.), being wide, carinate, 
pointed in front and forked behind, and has a semidistinct postero-lateral vomer 
(v”.) attached to the outside of each fork. 
The hard palate is well developed, three-fifths of it belongs to the maxillaries (mz.) 
and the rest to the palatines (pa.), which have their palatal plate very large, perfect, 
and typical ; yet the fore part of the median suture even of these bones is imperfect, 
and the vomer (v.) is partly exposed; the maxillaries meet each other nowhere, at 
present. The hinder and upper part of each palatine is a thick lobe of bone turned 
outwards, behind, and bevelled on its inner face for the pterygoid bone (pg.). A club- 
shaped cartilage adheres to the inferior surface of this small bone, the pointed end is in 
front and the clubbed end is turned outwards, behind ; this is the pterygoid cartilage 
(pg.c.), and is a genuine remnant of the endoskeletal upper jaw of a branchiate 
type. The broad hind skull is seen from this aspect, flanked and supported by the 
infero-lateral squamosals (sq.); the annuli (a.ty.) are seen as U-shaped bones—right 
and left—with their crura looking outwards and backwards, and their arch almost 
touching the pretympanic boss of the basisphenoid. These are all the investing 
bones that I can discover at this stage. 
The endocranium may now be described. I shall begin with the palatal (or basal) 
part first (Plate 26, fig. 5). Looked at, as a whole, this is a very solid cartilaginous 
structure, here and there undergoing ossification. The snout (a/.7.) with its inferior 
external nostrils (e.n.) has a length about a fourth greater than its breadth ; it is 
quite a continuous structure. The snout passes into the proper nasal labyrinth, not 
only above and at the sides, but the floor, also, sends backwards a remarkable tongue- 
like process—the recurrent or J Acopson’s cartilage (re.c.). This tract, right and left, is 
2A 2 
