Ichthyopsida 



423 



PAL^TOQUADRATE 



CESTRACION, A SHARK 



Fig. 325. The skeleton of an elasmobranch, Cestracion. (After Dean. Courtesy, 

 Neal and Hand: "Chordate Anatomy," Philadelphia, The Blakiston Company.) 



CCL Ctti) 



Fig. 326. Sagittal section of Squalus vertebrae, cut 

 surfaces obliquely lined, (c) Calcifications of centra; (cd) 

 caudineurals; (cdh) caudihemals; (crh) cranihenials; 

 (cr{i)) cranineurals (intercalaria) ; (rf) exits of dorsal 

 nerve-roots; (n) notochord; (») exits of ventral nerve- 

 roots. (Courtesy, Kingsley: "Comparative Anatomy of 

 Vertebrates," Philadelphia, The Blakiston Company.) 



Fig. 327. Tails of fishes. (A) Young Amid, skeleton. (B) Diphycercal. (C) 

 lleterocercal. (D) Homocercal. (h) Hypurals; (n) notochord; {s) spinal cord. 

 (Courtesy, Kingsley: "Comparative Anatomy of Vertebrates," Philadelphia, The 

 Blakiston Company.) 



