392 



rut: 



ATVRAL1ST [Tol.LII 



explained on this basis is extremely doubtful. It is cer- 

 tain!} nut true that all vertebrates exhibit indications of 

 such spasms. While complete skeletal remains of fossil 

 vertebrates are relatively rare, yet there is a sufficient 

 number preserved which have been described 1 to determine 

 the relative frequency of these positions. 



In the many complete skeletons of fossil reptiles from 

 the Eocene of France described by L. Lortet 8 only four, 



