CLASSIFICATION OF THE CEPHALOCHORDA. 



279 



only one species each, while a fourth, Asymmetron, has 

 two, one of which Willey 1 subsequently regarded as 

 merely a variety of the other. This gives us four out of 

 five sub-genera which are monotypic. Sub-genera at 

 most are merely groupings of species, and when each sub- 

 genus has but one species, their reality and convenience 

 may well be doubted. Moreover, their use indicates a 

 less close relation between the species than really exists. 

 For these reasons it is advisable to do away with sub- 

 genera in this group and to divide it simply into genera 

 and species. The classification would then be as 

 follows : — 



Order CEPHALOCHORDA. 

 Family Branchiostomid^e. 

 Gtenus I. Branchio stoma. 



B, lane eola turn. 



B. caribbceunu 

 rB. belcheri. ~~| 

 \_B. nakagawce.A 



B. calif orniense. 



B. elongatum. 



B. capense. 



B. indicum. 



B. pelagic tun. 



Genus II. Asymmetron. 



A> bassanum. 

 A. cin gale use. 

 A- hectori. 

 i A. maldivense. 

 A. cultellwm. 

 A. lucayanum ."] 

 A. caudatum. J 



[ 



In 1901 when he published his classification. 



