GENERAL OUTLINES OF ICHTHYOLOGY. 29 



The head in various species differs much in form, but in 

 general consists of the same number of bones as in other 

 vertebrate animals, viz. a frontal of six pieces, parietals of 

 three, occipitals of five, sphenoid of five, and two of each 

 temporal bone. 



Of these the most important to the naturalist are the 

 bones forming the gills, e,f, and g — and those constituting 

 the jaws, r, s, t, v, w, sc, y. 



Amongst the latter the inter- or pre-maxillary* {w) forms 

 in most fishes the edge of the front of the upper jaw, 

 having the maxillary [v] behind it. The situation of the 

 palatine-f bones (s) is in the roof of the mouth, one on each 

 side of the vomer X {t) ; and in the Perch both these bones 

 and \hQ pterygoid (r) carry teeth. The lower jaw, except 

 in the cartilaginous fishes, has generally two bones in each 

 side: a further reference to these bones will be found 

 under the division " Teeth." The bones to which the fins 

 are attached wiU be more conveniently noticed in the re- 

 marks on the latter organs. 



The relative positions of the bones composing the gill- 

 covers, or opercula §, will perhaps be more easily distin- 

 guished by a reference to the accompanying diagram of the 

 head of a Trout, in which 



* So named from the Latin maxilla, a jaw. 

 t Palatine bones, or bones forming tie palate. 

 % Vomer, so called from a fancied resemblance to a plouglishare, for 

 which the name given is the Latin. 



§ Opercula, from the Latin opercuhim, a lid or cover. 



