180 ORiaiNAL ARTICLES. 



AlfATOMT OF THE HeAD A^D ShOFLDEHS. 



(Pt. VI. fig. 1.) Tlie bones of the skull exhibit nothing very re- 

 markable in their number and relations, but present some peculiarities 

 of proportion. The supraoccipital bone lies a long way in front of 

 the back part of the basioceipital, and, on the other hand, the mouth 

 is projected forwards by the combined intermaxillaries being placed 

 entirely in front of the nasal (Owen's), not overlapping it, but moving 

 rather after the fashion of a parrot's beak. 



As regards the base of the skull : the basisphenoid is powerfully 

 developed, presenting considerable vertical thickness ; and the vomer 

 is very small, and lies underneath the fore part of the nasal. The 

 bones of the roof of the skull are particularly thick and spongy. Tho 

 supraoccipital and paroccipitals are small, and each developed into a 

 pointed process directed backwards. The nasal is broad and square, 

 and is inseparably attached to the anterior extremity of the 

 primordial cranium. Tlie great frontals lie quite free on the surface 

 of the latter ; and, as they present no serrated sutures, dro]) easily 

 separate from each other and the rest of the skull, when laid bare. 

 They form the greater part of the roof of the skull, and, projecting 

 as they do, as fiir back as the exoccipitals, they drive the postfrontals 

 and mastoids still further back. The latter extend back a long Avay. 



As regards the lateral wall : the exoccipitals, look almost directly 

 baclvwards and are perforated for the vagus ; and in front of tliem 

 is the disputed bone called alisphenoid by Professor Owen, petrous 

 by Professors Groodsir and Huxley, and wliich, in this instance,, is 

 perforated for the branchial nerve.* 



In front of this is a large foramen which transmits the trigeminal 

 and optic nerves ; and which is bounded above by the orbitosphenoid 

 of Owen — the alisphenoid of Goodsir and Huxley, and in front by 

 the mesially situated bone of the interorbital sej^tum, which, how- 

 ever, only invades the posterior half of the septum, the rest 

 remaining cartilaginous. 



The prefrontals are very far separated, being, on each side, in an 

 angle between the great frontal and nasal, and perforated, as usual, 



* For my own part, I am quite satisfied that the petrous hone of the cod is re- 

 pi'escntcd in tlie carp by that part of the cxoccipital whicli gives passage to the 

 branchial nerve, while in the sun-fish the same element, giving passage to the same 

 nerve, fomis one bone along with the alisphenoid, and is the posterior jiart of the 

 ■bone dcscril)cd in the text. This variation in the development of an osseous clement 

 is quite parallel to what we know with regard to the internnixillary bone in the 

 human subject, which is normally developed from the maxillary, but, in cases of 

 cleft palate, is found in front of the vomer. As to the detemiination of the ali- 

 sphenoid and orbitosi)henoid, 1 follow Professor Owen's view, being particularly 

 convinced of its accuracy by the arrangement in the skull of Jlalopterurus, where 

 the orbitosphenoid is rendered unquestionable by being conq>lctcIy jicrforated by the 

 optic nerve. — See Edinburgh New Philosophical Journal, October, 1858. 



