﻿8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 59 



always. It remains to be seen whether this is the origin of the 

 fissure in the present species.' Cope does not say whether he had 

 investigated the question when he established the genus Rhegnopsis 

 in 1896, though an investigation was much to be desired. From the 

 figures, which are diagrammatic sections of jaws, it appears that 

 Cope's ' Meckelian fissure ' in Tretulias and Rhegnopsis is nothing 

 more than an artificial crack. It is, at all events, entirely different 

 from the ' Meckelian fissure,' sulcus mylohyoideus, which, as a shal- 

 low canal, follows more or less the lower border on the inner side of 

 the jaw in various Right whales. Rhegnopsis is, in any case, of very 

 doubtful validity." (Op. cit, pp. 28-29.) 



