CLASSIFICATION 137 



to that of the Tunicata (see p. 55), but lends no support to 

 the view that Amphioxus has degenerated from a higher group 

 of the Vertebrata. 



Classification of the Cephalochordata. 



The known species of Amphioxus may be classified as 

 follows l : 



FAMILY BRANCHIOSTOMATIDAE. 

 Genus 1. Branchiostoma (Costa, 1834). 



Having biserial gonads and symmetrical metapleura. 



B. lanceolatum (Pallas) Myotomes 36 + 14 + 12, gonads 23-29 pairs: 



Mediterranean, N.W. Europe, Ceylon, E. of United States. 

 [B. belcheri, Gray Myotomes 38 + 17 + 9: Torres Straits, Singapore, 



Borneo, Ceylon. 



[.B. nakagawae, Jord. and S. Myotomes 37 + 16 + 11 : Japan. 

 [B. caribbaeiim, Sundevall Myotomes 37 + 14 + 9 : West Indies, Atlantic, 



N. and S. America. 



B. capense, Gilchrist Myotomes 47 + 19 + 9: S. Africa. 

 B. californiense, J. G. Cooper Myotomes 45 + 17 + 9 : California. 

 B. (Dolichorhynchus) indicum (Willey) Myotomes 42 + 14 + 15: India 



and Ceylon. 



(?) B. elongatum, Sundevall Myotomes 49 + 18 + 12: Peru. 

 (?) B. pelagicum, Giinther Myotomes 36 + 16 + 15: Honolulu, Gu'.f of 

 Manaar, South Indian Ocean. 



Genus 2. Asymmetron (Andrews, 1893). 

 "With uniserial (right) gonads and asymmetrical metapleura. 



A. lucayanum, Andrews Myotomes 44 + 9 + 13: Bahamas, Maldives, 



Zanzibar. 



A. caudatum (Willey) Myotomes 40 + 9 + 11 : Louisiade Archipelago. 

 A. (Heteropleuron) bassanum (Giinther) Myotomes 45 + 16 + 14: Bass 



Straits, Australia. 



cingalense (Kirkaldy) Myotomes 39 + 16 + 8 : Ceylon. 



cultellum (Peters) Myotomes 32 + 10 + 10 : Torres 



Straits, Australia, Ceylon. 



' maldivense (F. Cooper) Myotomes 45 + 16 + 12 : Mai- 



dive Archipelago, Zanzibar. 



hectori (Benham) Myotomes 53 + 19 + 12 : New Zea- 



land. 



1 I have to thank Mr. Walter Tattersall, B.Sc., working in my laboratory, for 

 a detailed summary and discussion of the various published schemes from which 

 this table has been drawn up. He has also filled up for me the map (Fig. 90) 

 showing the geographical distribution of the species. (See also Trans. Biol, Soc. 

 Liverpool, vol. xvii. 1903, p. 269.) 



