OF THE SKULL IN THE COMMON SNAKE. 
411 
which cleaves to the post-frontal projection of the large parietal bone — a remarkable 
state of things certainly, but the parietals are prepotent in the Snake’s skull. 
The foremost fourth of the skull belongs to the olfactory region : the essential 
parts here are most simple, the superadded things are as curiously complex as anything 
to be found in Vertebrate morphology.* 
The fore end of the Snake’s skull is composed of the following elements, viz. : 
(a.) The coalesced vertical part of the trabeculae, and 
(h.) The nasal roof- cartilages (sense-capsules) grafted thereupon. 
(c.) The short confluent trabecular cornua, — the rudiment of a terminal visceral 
arch (first pre-oral). 
(cZ.) Attached to, or partly coalesced with these cornua, two pairs of upper labial 
cartilages. 
(<?.) Nine membrane-bones, of which the odd one, the premaxillary, is the splint of 
the cornua, the nasals or splints of the olfactory roof, the prefronto-lachrymals or 
splints of the postero -lateral region of the nose, and the septo-maxillaries and vomers, 
which are related to the middle wall of the nasal capsules. 
(f. ) Lastly, there are the huge nasal glands, that are encapsuled in the last-mentioned 
bones. 
(a.) The form and relations of the septal portion of the trabeculae are shown in the 
lateral view of the bisected skull (Plate 33, fig. 1, s.n.), and in the series of transverse 
sections (Plate 33, figs. 6-14, s.n.). 
This wall is highest where the olfactory cartilages are united to it, behind, and 
lowest in front when the roof cartilages overlap it (fig. 6). 
(b.) The nasal cartilages (ol.) are quite simple ; I find no turbinal outgrowths in them 
whatever. 
They are only imperfectly covered by bone (Plate 32, fig. 1) ; they turn inwards below 
in some degree, especially behind (Plate 33, fig. 4, n.f), forming at the beginning of 
the septum a partial floor. 
They are baggy in front (Plate 33, fig. 5), and notched externally for the nostril 
(Plate 32, figs. 1 and 3, and Plate 33, figs. 2 and 5). 
( c .) The recurrent cornua are very short and have a median rudiment of the pre- 
nasal cartilage (Plate 32, fig. 3, c.tr., p.n.) ; I found, in that specimen, the left cornu 
confluent with the first upper labial (u.l 1 .). 
* My study of these structures in the Snake began ten or twelve years ago, during which time I have 
had frequently to refer to them in the descriptions of their homologues in other types, especially in the 
Birds, so far above them. The reason of the delay as to this paper has been the slow incoming of embryos 
young enough for my purposes. 
Now, however, I can show a sort of practical standard, towards which the Ganoid and Teleostean 
Fishes and the Amphibia ascend, and from which the higher Reptiles and the Birds take their start. Of 
course I speak of the use of this Ophidian standard as an arbitrarily practical matter, and I do not wish 
to suggest anything except in a general way as to the actual descent of these Vertebrate types. 
