242 VERTEBRATE ANIMALS. 
Haddock family (Gadide), and the Flat fishes (Pleuronectide), compris- 
ing the Sole, Turbot, Flounder, and others. 
SUB-ORDER III. ACANTHOPTERI,—Fins with one or more of the 
first rays in the form of undivided, inflexible, spinous rays. Scales mostly 
ctenoid. Swim-bladder without a duct. 
The leading families in this order are the Wrasses (Cyclolabride), the 
Perches (fercide), the Mackerels (Scomberide), the Mullets (Alugiiide), 
and the Gobies (Godzzde). 
SUB-ORDER IV. PLECTOGNATHI.—Certain of the bones of the mouth 
(the maxillary and pree-maxillary bones) immovably connected on each 
side of the jaw. Integumentary skeleton in the form of ganoid plates, 
scales, or spines. . 
The chief families in this sub-order are the File-fishes (Balistide), 
and the Trunk-fishes (Ostractontide). 
SUB-ORDER V. LOPHOBRANCHII.—Gills arranged in little tufts on 
the branchial arches. Integumentary skeleton in the form of ganoid 
scales. 
The two families contained in this division are the Sea-horses (HzAfo0- 
cunipide), and the Pipe-fishes (Syuguathide). 
ORDER IV. GANOIDEI (Gr. gavos, splendour, or brightness).— 
The fourth order of fishes is that of the Gaozdez, including few 
living forms, but having a great and varied development in past 
geological epochs. The Ganoid fishes are distinguished by the 
imperfect development of the skeleton, which is mostly cartila- 
ginous throughout life, and by having an integumentary skeleton 
composed of ganozd scales, plates, or spines (fig. 122, @). The 
skull is composed of distinct bones, and there is always a lower 
jaw. ‘There are usually two pairs of fins (pectoral and ventral), 
supported by many series of cartilages, and the ventral fins are 
placed very far back. The first rays in the fins are usually in 
the form of strong spines. The caudal fin or tail is mostly 
heterocercal or unsymmetrical (fig. 125, 4). The swim-bladder 
is always present, is often cellular, and is provided with an air- 
duct. The gills and gill-covers are essentially the same as in 
the bony fishes. The heart has oneauricle and a ventricle ; and 
the dulbus arteriosus is rhythmically contractile, is furnished 
with a distinct coat of muscular fibres, and is furnished with 
several transverse rows of valves. 
The best known of the living Ganoids are the Bony Pike 
(Lefidosieus), the Sturgeon (S¢urzo), and the Polypterus. Of 
these, the Bony Pike is found in the rivers and lakes of North 
America. Itis a large fish, attaining a length of several feet, 
