STRUCTURES OF TELEOST 141 



General Anatomy 



In the Teleost (Fig. 145) the shortened and muscular 

 body appears admirably adapted to the conditions of 

 aquatic motion. Anteriorly it is broad and deep, its 

 trunk muscles firmly attached to the bony prongs of the 

 enlarged base of the skull, DCR, and to the solid, compact, 

 calcified vertebrae, V, and their stout processes. The 

 fish's tapering sides are encased in horn-like cycloidal 

 scales, CS, a light, flexible armour, whose elements over- 

 lap, defending every point, and whose smooth and slime- 

 coated surface provides the least possible resistance to 

 motion. The fins, D, C, A, PF, VF, are light and strong, 

 erectile and depressible; their rays are thin, narrow, spine- 

 like, strong ; they ai e entirely dermal, their cartilaginous 

 supports sinking within the body wall, RB. The caudal 

 is large and fan-shaped (homocercal), its crowded rays 

 providing admirably its needed strength ; its stout basal 

 supports, compacted beneath the tip of the notochord, NC, 

 show that its form is modified heterocercy. The pectoral 

 fin, PF, has now taken its position high in the side of the 

 body ; its basi-radial supporting elements are reduced to a 

 proximal row of a few small irregular plates. 



The skeleton is completely calcified. The vertebral axis 

 has undergone entire segmentation, the notochord persist- 

 ing only between the cup-shaped faces of the centra ; the 

 vertebral arches and processes have merged with the 

 centra, and those of the hinder region, A\ H, with prob- 

 ably the basal fin supports as well. Ribs, R, usually with 

 intersupporting processes, strengthen the walls of the 

 visceral cavity, and represent calcifications of the myocom- 

 mata, rather than transverse processes of the vertebrae. 

 The skull is formed of compact bony elements ; its carti- 



