BONY FISHES AND GANOIDS. 471 



in number, or replaced by keeled plates, and in all the dorsal fin is single, 

 with but few spines. In form, the compressed body is deep or oblong, the 

 scales with which it is invested being minute, while the eyes are lateral and 

 of moderate size. The mouth is small, and armed with compressed incisor- 

 like teeth, which may be either serrated or pointed, bub teeth are never 

 developed on the palate. The pelvic fins are situated thoracically. Inter- 

 nally, a peculiarity is to be found in the forked hinder extremity of the air- 

 bladder. These fishes, which also include the genera Naseus and Prionunis, 

 are inhabitants of tropical seas, and specially frequent coral-reefs. Here 

 they feed partly on the growing coral and partly on vegetable substances. 



The secorid family of the section under consideration includes — among 

 other forms — the horse-mackerels (Caranx), the pilot-fish {Naucrates), and 

 the so-called sea-bats (Platax). In all of these the body is 

 more or less compressed in form, while the teeth, when Family 



developed, are conical, and there is aio bony connection Cara7igidce. 

 between the preopercular bone and the orbit. The skin 

 may be either naked or covered with small scales, and the eyes are placed on 

 the sides of the head. The spinous dorsal fin is shorter than the anal or soft 

 dorsal, from the latter of which it is sometimes separated, while in other 

 cases the two are continuous. In some cases the spinous portion is rudi- 

 mental, and the hinder part of both the soft dorsal and anal may form finlets, 

 while the pelvics, if developed at all, are thoracic. It is important to notice 

 that the back-bone comprises ten vertebra in the region of the trunk, and 

 fourteen in that of the tail, although in one case the number of the latter is 

 sixteen. Frequently shield-like plates distinguish the lateral line. An air- 

 bladder is invariably developed. The horse-mackerels — as typified by the 

 common scad — are too well known to require description, while the pelagic 

 pilot-fish may always be recognised by the dark vertical stripes with which 

 the body is ornamented. This fish derives its narrie from its habit of accom- 

 panying sharks or ships. In the preceding genera there are two anal spines 

 remote from the soft portion of the fin ; but in the sea-bats the anal spines 

 are continuous with the soft part, when present. These fish have the body 

 very deep, and rhomboidal in form, and the great development of the median 

 fins, which are often nearly similar above and below. In common with the 

 great majority of the family, the three genera mentioned have the soft dorsal 

 and anal fins of nearly equal extent, but in ChHus and Fempheris there is only 

 a single dorsal, which is much shorter than the anal. 



The ugly but excellently flavoured John-dory {Zevs faher) is the best known 

 representative of a small family distinguished from the other members of the 

 section by the deep and highly compressed body, the double 

 dorsal fin, and the presence in the backbone of more than Family 



ten trunk and more than fourteen caudal vertebras. In the Cyttidm. 



fishes of the genus named one series of bony plates runs 

 along the base of the dorsal and anal fins, and another on the abdomen, but 

 in the species of Cyttus — which inhabit the seas of New Zealand, South 

 Australia, and Madeira — these plates are wanting, and the body is scaled. 



The small family of the Stromateidce resembles the last in the absence of a 

 bony stay between the preopercular and the eye, and likewise in the large 

 number of thoracic and caudal vertebrae. They have the 

 body compressed, more or less oblong, and covered with Family 



minute scales, the eyes lateral, the dentition very slightly Stromateida:. 

 developed, and a number of horny barbed processes in the 



