6 University of Michigan 



eight specimens; average 42). Highest dorsal ray-chambers, 

 in each individual, only one to two times as high as long; 

 dorsal fin about one-eighth as high as body. Anus located 

 well in advance of middle of lower lobe of caudal fin; distance 

 from atriopore to origin of lower caudal lobe exceeding the 

 distance thence to end of tail. Pre-atrioporal length of body 

 2.0 to 2.6 (usually 2.3) times as great as the postatrioporal 

 length. Myotome formula: 34 to 384-12 to 16+10 to 13= 

 58 to 64. Gonad pouches 21 to 29 (Kirkaldy). IMaximum 

 length, 5.8 cm. (Kirkaldy). 



5. Brancliiostoma helcheri Gray 



Amphioxus helcheri Gray (1847); Kirkaldy (1895). 



Brauchiostoma belcheri Gray (1851) ; Andrews (1893) ; Willey 

 (1894); Herdman {1904); Lonnberg- (1904); Jordan, Tanaka and 

 Snyder (1913)- 



Brancliiostoma, sp. Andrews (1895). 



Amphioxus, sp. Nakagawa (1897). 



Amphioxus belcheri japonicns Willey (1897). 



Brauchiostoma nakagazi'ae Jordan and Snyder (1901). 



Brauchiostoma lanceolatum belcheri Tattersall (1903). 



Amphioxus japonicns Lonnberg (1905). 



This species has been satisfactorily distinguished from B. 

 lanceolatum by Kirkaldy and by Tattersall, on the basis of 

 dififerences in the form of the rostral and caudal fins. In gen- 

 eral proportions it agrees closely wMth that species. The pre- 

 atrioporal length of the body is contained 2.1 times in the 

 postatrioporal length in the type of B. nakagazvae. 



6. Branchiostoma carihaeum Sundevall 

 Brauchiostoma caribacum Sundevall (1853), and other authors (in 

 part). 



Diagnosis: — This lancelet, which apparently is restricted in 

 its distribution to the West Indies, may be distinguished by 

 the following set of characters, all determined, with the excep- 

 tion of the myotome formula, from two small specimens from 



