2 7 8 



ELEMENTARY ANATOMY. 



[LESS. 



so are quite unlike the scales of Reptiles. Indeed, the 

 " scales" of Fishes should rather be termed "scutes." 



They have been divided into two groups or kinds those 

 in which the free margin is smooth and which are termed 



FIG. 257. A SHACKLE-JOINT. 



Articulation of a large spine with a bony plate (placed below) of the skin of a 

 Siluroid Fish. 



Cycloid* and those in which the free margin is toothed and 

 which are named Ctenoid? 



37. Besides scales, spines, and plates, Fishes have OTHER 

 DERMAL STRUCTURES, bony or gristly, constantly present 

 within the dermis. One kind consists of filamentary pro- 

 cesses, which may be either horny or calcareous, and which 



FIG. 258. DORSAL FIN OF AN ACAN- 

 THOPTERYGIAN FISH, showing the 

 firm, spiny fin-rays, f, supported on 

 the inter-spinous bones, i. 



FIG. 259. DORSAL FIN OF A MALA- 

 COPTERYGIAN FISH, showing the soft 

 and sub-divided fin-rays, f, sup- 

 ported on the inter-spinous bones, i. 



support the skin of the fins, whether those of the back, belly, 

 and tail, or those of the limbs. Such structures are termed 

 fin-rays. Another kind consists of the parts (bony or gristlv) 

 which support the fin-rays, and which are termed the "i?iter- 

 spinous" bones or cartilages. These may be seen in the 

 common Sole in the form of small bones extending along 

 each margin of the body beyond the ends of the neura- 

 pophysial and hypapophysial processes which respectively 

 project in opposite directions from the centre of the backbone. 



1 From KI'IK\O, a circle, and ei'5<>r, form. 



2 From KTCC, a comb, and eido. 



