IV. 



VERTEBRATA: PISCES, TELEOSTEL 



5T1 



Order III. Acanthopteri (Acanthopterygii). 

 This is the hirgest group of fishes, its members usually having 

 the ventral fins thoracic in position and more than three raj's spiny 

 in dorsal, anal, and ventral fins. The sticklebacks (Gasteku- 

 STEiDiE) and some other forms have the pharyngeal bones reduced, 

 the ventral fins farther back, and form the grouji Ilemibranchii. 

 Gnsterosteus.* The perch of fresh water (Perciu^), Perca* 

 and MirA'optems* (black bass), and the marine Serkanid^, some 

 of which are hermaphroditic, have ctenoid scales. The Scombeid^t:, 

 with Scomber* the mackerel, and Tliynnus* the horse mackerel, and 



Fio. 605- — Scumhcr s<:i>mhru!^y mackerel. 



the Xii'iiiiD^i;, or sword fishes, in which the snout is jirolonged into 

 a long sword, are the most important edible fishes of the group. Tlie 

 Lcji'.iuATi, including the sculpins {Coitus,* Hemitripterus,* fre- 

 quently have the body armored with Ijony plates. The Emistotocid^e, 

 or surf perches of the Pacific, are viviparous. Tlie suck fishes, 

 Remora,* Echeiicix,'" have the first dorsal modified into a sucker on 

 the top of the head. 



Order IV. Anacanthini. 



These are soft-finned fishes in which the ventral fins lie in 



Fig. dOG.—Gadus morrhva,* cod. (After Storer.) 



front of the pectorals. Structure goes to show that these have 

 descended from Acanthopteran forms. With few exceptions 



