686 FISHES. 



velvety appearance to the skin (Figs. 17 and 18, p. 48). Adult 

 males of some of the species possess a peculiar armature on 

 each side of the tail, which in females is much less developed 

 or entirely absent. This armature may consist either in 

 simple spines arranged in rows, or in the development of the 

 minute spines of the scales into long stiff bristles, so that the 

 patch on each side of the tail looks like a brush. 



C. OSTRACIONTINA. — The integuments of the body form a hard 

 continuous carapace, consisting of hexagonal scutes juxtaposed 

 in mosaic-fashion. A spinous dorsal and ventral fins are absent; 

 but sometimes indicated by protuberances. 



The " Cofter-fishes " (Ostraciofi) are too well known to 

 require a lengthened description. Only the snout, the bases 

 of the fins, and the hind part of the tail are covered with soft 

 skin, so as to admit of free action of tlie muscles moving these 

 parts. The mouth is small, the maxillary and intermaxillary 

 bones coalescent, each jaw being armed with a single series 

 of small slender teeth. The short dorsal fin is opposite to the 

 equally short anal. The vertebral column consists of fourteen 

 vertebrae only, of which the five last are extremely short, the 

 anterior elongate. Eibs none. The carapaces of some species 

 are three-ridged, of others four- and five-ridged, of some 

 provided with long spines. Twenty-two species from tropical 

 and sub-tropical seas are known. 



Second Family — Gymnodontes. 



Body more or less shortened. The hones of the upper and 

 lower jaw are confluent, forming a teak ivitli a trcnehant edge, 

 loithout teeth, with or without median suUire. A soft dorsal, 

 caudal and anal are developed, approximate. No spinous 

 dorsal. Pectoral fins ; no ventrals. 



Marine fishes of moderate or small size from tropical and 

 sub-tropical seas. A few species live in fresh water. Fossil 

 remains of Diodon are not scarce at Monte Bolca and Licata ; 



