136 LECTURE VI, 



the turbinate bone, to wliicb it is attached by ligament, and it 

 is articulated by its upper and posterior angle with the pre- 

 frontal : from its position it might be termed the pre-orbital bone. 

 The second sub-orbital, a much smaller and sub-quadrate bone, is 

 attached to the lower and posterior angle of the first ; and the rest, 

 four in number, of similar form, and gradually smaller in size, com- 

 plete the chain extending to the post-orbital angle of the os frontis. 

 There are no supra-orbitals in the Cod : the Carp has a single one on 

 each side ; the Lepidosteus has three supra-orbitals, which quite 

 exclude the frontal from entering into the formation of the orbit. 

 The supra-temporal scale bones are three in number on each side in 

 the Cod, extending backwards from the outer and hinder part of the 

 mastoid : they are very thin, transparent scales, folded on themselves 

 to form a prolongation of the mucous channel, which extends from 

 above the mastoid and frontal bones. The large pre-orbital scale- 

 bone is similarly folded uj)on itself, from above downwards, forming 

 a mucous channel, extending from the orbit to the nasal sac, and 

 analogous to the muco-lachrymal groove and canal in the lachrymal 

 bone of higher Vertebrata, which always presents a similar position 

 and connections. The smaller sub-orbitals are subservient, chiefly, 

 to the formation of similar mucous ducts, which are completed in 

 these, as in the supra-temporals, by aponeurotic processes of the 

 corium, and are lined by mucous membrane continued from many 

 small and numerous excretory pores on the outer surface of the 

 skin, and forming, in the Cod, ramified secreting follicles in the in- 

 terior of the bony canals. The bony canals themselves are ramified 

 in the corresponding dermal ossicles of the Herring. The turbinate 

 bones, from their intimate relation with the olfactory sacs, appertain 

 by their form and structure to the same category as the sub-orbitals, 

 and are, with the anterior of these mucigei'ous ossicles, the only bones 

 of the dermal system constantly retained in the higher Vertebrata, 

 even to Man, under the names of ' lachrymal' and ' spongy' bones. The 

 turbinate bones are very small in the Conger ; and both these and the 

 sub-orbital bones are wanting in the rest of the Eel tribe. The sub- 

 orbital bones present their maximum of development in the Mailed- 

 cheeked ( T/%/a) and Scia3noid Fishes; in the Star-gazer (f7"/-«»o- 

 scopus) and the Lepidoleprus : in the Scicena ganc/etica they extend 

 over the tympanic pedicle almost to the pre-opercular, and have a 

 bold reticulate exterior, like that bone, the mastoid, and the supra- 

 scapular bone. 



In the skull of the Cod you may observe many bones which send a 

 scale-like process from their outer surface, which process forms a more 

 or less complete canal for tlie ducts of mucous glands. The frontal, the 



