No. i.] 



INTERCALATION OF VERTEBRAE. 



47 



The most striking case of increase of presacral vertebrae dur- 

 ing the ontogeny of one species is shown by Branchiosaitrns 

 ainblystonins Creel., a Stegocephalian from the Permian of Ger- 

 many. The number of the presacral vertebrae is smaller in 

 the younger specimens, and gradually increases until the adult 

 stage is reached. Credner ('86, p. 620) gives the following table : 



We have here the highest number of sacral variations that 

 has been observed. 



Having considered the Amphibia, we may now pass over to 

 the Reptilia. Hyrtl ('64, pp. 264-272) has described in 1864 

 asymmetrical sacra in the following lizards : LopJiura amboi- 

 ncnsis Schlosser, Amphibolurus (Grammatophord) barbatitsC\\v., 

 and Tnpinanibis (Ctcnodon} nigropunctatus Spix. In the living 

 Crocodilia the number of the presacral vertebrae is 24, which 

 are all procoelous or concave-convex. There are two sacrals: 

 the first one is concave-plane, the second plane-convex, and the 

 first caudal is biconvex; all the following caudals are like the 

 cervicals, procoelous. 



