270 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Genus II. Heteropleuron. 



Sub-genes I. Paramphioxus, e.g., P. bassanum. 

 Sub-genus II. Epigonichthys, e.g., E. cultellus. 

 Sub-genus III. Asymmetron, e.g., A. lucayanum. 



A criticism of this, as well as the other classifications, 

 will be given later. In the same journal Benham also 

 described a new species of Acraniate, Heteropleuron 

 hectori, from New Zealand which had been laid by in a 

 museum for twenty years labelled A lanceolatus. Its 

 myotome formula is 53, 19 (20), 12. In the same year, 

 1901, Jordan and Snyder 1 made a new species B. naka- 

 gaweE for a Japanese lancelet. In 1902 F. Cooper 

 described a new species of Heteropleuron, H. maldivense, 

 from the Maldive and Laccadive Islands. It resembled 

 H. bassanum in its myotome formula and H. cultellum 

 in general shape. Its formula was 45, 16, 12. In 1902 

 also, a new species, B. capense was recorded from South 

 Africa by Gilchrist, 2 with the formula 47, 19, 9. 



Such is the history of all the known species of the 

 group. We shall now consider the various classifications. 

 Taking Gill's first we can dismiss it in a few words. 



The differences between his different genera do not 

 appear to me to be of equal value for while Br anchio stoma 

 differs from Paramphioxus in the character of such im- 

 portant and constant organs as the gonads, Paramphioxus 

 differs from Epigonicldhys only in such variable and 

 unsatisfactory points as the shapes of the fins. Moreover, 

 his diagnosis of the genus Amphioxides is neither definite 

 nor accurate, for Gunther distinctly states that B. pela- 

 gicum has a ventral fin but no fin rays. While 

 Branchiostoma and Amphioxides are certainly distinct 

 from the other three genera, they cannot be considered 



1 Proc. U.S. Nat. Museum. Vol. xxiii., No. 1233. 

 2 Marine Investig. S. Africa. Vol. ii., No. 7. 1902. 



