118 ANATOMY OF VERTEBRATES. 



the upper, usually bifurcate, end of the maxillary, forms a socket 

 on which the ascending or nasal process of the premaxillary 

 glides ; a posterior tubercle at this end is attached to the palatine, 

 and ligaments connect the same expanded end to the nasal, the 

 turbinal, the vomer, and the premaxillary : the lower and hinder 

 expanded end of the bone is attached by strong elastic ligament, 

 in which a labial gristle is commonly developed, to the lower jaw. 

 In the Salmon and Herring tribe, the Sudis, fig. 86, 21, Amia, 

 and most Ganoids, the maxillary supports teeth. In the Plecto- 



gnathi (Globe-fish and File-fish), the 

 maxillaries coalesce wholly or in part 

 with the premaxillaries. In the Lepi- 

 dosteus the contrary condition prevails : 

 the premaxillary and maxillary bones 

 constitute, indeed, a single dentigerous 

 arch or border of the upper jaw, as in 

 Disarticulated bo.es of paiato- % 86, but are subdivided into many 



maxillary arch (Arapaimagigas) bony pieces, a Condition which SCCmS tO 



have prevailed in some of the ancient extinct ganoid fishes. In 

 the Polypterus the maxillary is large and undivided on each side ; 

 it supports teeth, and sends inward a palatine plate to join the 

 vomer and the palatine bone ; thus acquiring a fixed position and 

 all the normal features of the bone in higher animals. The 

 maxillary bone is very diminutive in the Siluroid fishes, and 

 appears, with the premaxillary, to be entirely wanting in certain 

 Eels (MurcenidcB). 



The premaxillary (haemal spine of nasal vertebra, figs. 75, 81, 22), 

 one of a symmetrical pair in the Cod and most other osseous fishes, 

 is moderately long and slender, slightly curved, expanded and 

 notched at both extremities : the anterior end is bent upward, 

 forming the nasal process, and is attached by lax ligaments to the 

 nasal bone and prenasal cartilage, to the palatine, and to the 

 anterior ends of the maxillary bones. The premaxillaries are 

 movably connected to each other by their anterior ends ; the nasal 

 processes are separated by the prenasal cartilage, the lower or 

 outer branches project freely downward and outward, fig. 75, 22 : 

 the labial border of each premaxillary is beset with teeth, whilst 

 the maxillary bone is quite edentulous in most osseous fishes, as 

 in the Cod, ib. 21. In Dioclon the premaxillaries and their 

 lamellated dental apparatus coalesce and constitute a single sym- 

 metrical beak-shaped bone : the premaxillary is also single in 

 Mormyrus. The confluent premaxillaries constitute the sword- 

 like anterior prolongation of the snout in Xiphias, and are firmly 



