THE SKULL OX^ OSSEOUS FISHES. 107 



into many bony pieces, a condition wliicli seems to have prevailed 

 in some of the ancient extinct Salamandroid fishes ; for example, the 

 genus of the Old-Red- Sandstone, which I have called Dendrodus. 

 In the PoJypterus the maxillary is large and undivided on each side ; 

 it supports teeth, and sends inwards a broad 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 (^Murcenidm). 



The j)rcmaxiUary, or intermaxillary bone (hajmal spine of nasal 

 vertebra, Jig. 30, 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 

 upwards, 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 maxillaiy bones. The premaxillaries are 

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

 processes are separated by the prenasal cartilage, the lower or outer 

 branches project freely downwai'ds and outwards : 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. By those 

 who may regard the prenasal cai'tilage as a vestige of a fifth cranial 

 vertebra the premaxillaries may be viewed as its inferior arch : but such 

 an arch would be incomplete, widely open ; the piers or crura diverg- 

 ing, instead of converging, to unite, like other inferior or haemal 

 arches. In the Diodon the premaxillaries and their lamellated dental 

 apparatus coalesce and constitute a single symmetrical beak-shaped 

 bone : MvAller also found a single premaxillary in the Mormyrus. 

 The confluent premaxillaries constitute the sword-like anterior pro- 

 longation of the snout in Xiphias, and are firmly and immovably 

 articulated with the pre-nasal and maxillary bones, in both the 

 Sword-fish and the Garpike. The premaxillaries are commonly 

 more extended in the transverse than in the vertical direction, which 

 latter most prevails in Mammals : but there are many examples in 

 Fishes where their development is equal in both directions. The 

 vertical extension, which forms the nasal branch of the premaxillary, 

 is of unusual length in the fishes with protractile snouts, as, for ex- 

 ample, in the Picarels (Mcnidcc), the Dories (Zeus), and in certain 

 "Wrasses, as Coricus, and especially the Epibulus, or Sparus in- 

 sid'uifnr of Pallas {Jig. 37, 22).* In this fish the nasal brancli of 



* Sec Ciivior and Yaloneicnncs, Hist, dor, Poissons, t. xiv. p. 02. The liypo- 

 tyinpanic or suspensory pedicle of tlie lower jaw is tlu re called llie ' nintar ' bone. 



