190 



LOWER VERTEBRATES. 



extremely young, preopercular spines and a dorsal fin are developed ; this stage has 

 been described as a peculiar generic type, under the name jy^aiiclerus ; these spines, 

 however, are soon lost. In extreme old age, the black bands are lost, and the fish is 

 then nearly uniform in color. 



Nearly related to the pilot-fish are certain forms which are known under the name 

 of amber-fishes, rudder-fishes, and madregals. These belong to the genus iSeriola. 

 In form and coloration they essentially resemble the pilot-fish ; but the spinous dorsal 

 fin is always developed, and has generally seven spines. One species of the genus, the 

 Seriola dorsalis, occurs along the southern Californian coast, and reaches a length of 

 four or five feet, and a weight of from thirty to forty pounds. It is highly esteemed 

 when fresh, but more especially when of moderate size, for large individuals are quite 

 coarse and tough. It is also prized when salted and dried, and as a cured fish is con- 

 sidered to be inferior to none put up on the Pacific coast. It is chiefly caught by 

 trolling. Several species occur on the Atlantic coast. 



The name dolphin, formerly associated with the cetaceous mammals now better 

 known as porpoises, has been transposed by our modern sailors to fishes related to the 



Fig. 113. — Naucrates ductor, pilot-fish. 



mackerels, and the forms so known belong to a peculiar family named Coryph^nid^. 

 These have a rather peculiar form, being largest and highest at the head, and thence 

 quite regularly diminishing to the slender tail. The back has a single fin extending 

 from tlie nape behindwards, and only the foremost rays are spinous. The caudal fin is 

 large and powerful, furcate, and running out into pointed lobes. The ventrals are 

 thoracic, or somewhat anterior. The adult males, at least, have a very prominent 

 forehead. The species exhibits brilliant, iridescent colors when first caught ; and the 

 changes in hue manifested by a dying fish have been celebrated by naturalists 

 and poets. The species are quite large, reaching several feet in length, and are 

 chiefly inhabitants of the open seas. They are often caught by the sailors in mid- 

 ocean, and are generally excellent as food ; their flesh is, however, liable to become 

 poisonous under certain circumstances, and, according to Mr. Goode, " It is an almost 

 universal custom before eating them to test the flesh by putting a piece of silver into 

 the vessel in which they have been cooked, it being a common belief that, if the fish is 

 poisonous, the silver will turn dark." The number of the species is uncertain ; but 



