Pigs. 44-48. Evolution of caudal fin. 44. Embryonic caudal of Amia. 45. Hetero- 

 cercal caudal of shark, Cestracion. 46. Heterocercal caudal of Cladoselache, 47. Diphy- 

 cercal caudal of Polypterus. (After L. AGASSIZ.) 48. Homocercal caudal of Teleost. 

 (After RYDER.) 



D. Dermal fin supports. L. Lateral line. M. Spinal cord. MC. Membranous caudal. 

 N. Notochord. N-\-, and R-\-N. Neural spines, including probably radial and basal 

 elements. R. Radials. R-\-H. Haemal arch and spine ; includes as well, probably, radial 

 and basal elements. 



37 



