SKIN, SCALES, AND SPINES 97 



whole head and body is strongly compressed, and is com- 

 pletely encased in a transparent bony cuirass with a knife-like 

 lower edge. This is made up of a number of thin plates, fused 

 with the underlying ribs in much the same way as the carapace 

 of a tortoise (Fig. 42H). In the Pipe-fishes {Syngnathidae) the 

 scales are replaced by a series of jointed bony rings, encircling 

 the body from behind the head to the tip of the tail. Similar 

 rings surround the prehensile tail of the Sea Horse {Hippocampus), 

 but in the immobile trunk region they take the form of plates 

 which are roughly cruciform in shape, and are interlaced with 

 one another to form a complete outer skeleton. The edges of 

 these plates are not infrequently produced into pointed spines 

 or rounded knobs (Fig. 5E). 



The bottom-Hxing Bat-fishes {0 gcocephalus) have the upper 

 surface of the body studded with spines or tubercles, not 

 unlike the scales of the Snipe-fishes in structure, but lacking 

 the pulp cavity, the projecting spine being soHd (Fig. 400). 

 Similar tubercles are sometimes found in the deep-sea Angler- 

 fishes or Ceratioids, but these fishes mostly have a naked skin. 

 In the Trigger-fishes (Balistes) the rough scales covering the 

 body are Hke those of the Bat-fishes, the basal plate often being 

 rhomboid in shape, with the outer surface roughened or armed 

 with one or more small spines (Fig. 420). In the File-fishes 

 (Monacanthus) the spines are more numerous, and are set so 

 close together as to give the skin the appearance of velvet. In 

 the allied family of Trunk-fishes (Box-fishes, Coflfer-fishes, 

 Cuckolds) a complete and sohd coat of mail again occurs. The 

 scales are represented by large six-sided plates, united with one 

 another to form a strong, bony box, from one end of which 

 projects the mouth and from the other the naked tail. This 

 box may be three, four, or even five-sided, and one or more of its 

 edges may be armed with strong spines (Figs. 5B; 42F). A West 

 Indian species {Lactophrys tricornis) , with two long spines projecting 

 forward from the forehead, is appropriately named the Cow- 

 fish. The little Pine-cone fish (Mo/zoc^wto), although pertaining 

 to a totally different order of fishes, is another form in which the 

 thick scales unite to enclose the body in a sort of box (Fig. 42E). 



The Surgeon-fishes ( Teuthidae) of tropical seas derive their name 

 from the presence of a lancet-like spine on either side of the fleshy 

 part of the tail. When not required this is retracted into a sheath 

 in the skin, but can be quickly turned outwards and forms an 

 effective weapon when the fish lashes its tail from side to side. 



In the Puflfers or Globe-fishes {Tetrodontidae) the scales are 



