CLASSIFICATION OF THE CEPHALOCHORDA. 299 



with fin chambers which may or may 

 not have fin rays, oral cirri when present 

 have sense papillae, atrial chamber pro- 

 longed behind the atriopore in a single 

 right ccecum. 

 (A) Species having oral cirri. 



(i.) in which pre-oral lobe is normal. 



(a) Myotomes 58-66- 



B. lanceolatum — average length 48 

 mm. ; myotomes 58-62 ; average 

 formula 36, 14, 12 ; rostral fin 

 small; 12 intra-buccal tentacles; 

 ventral fin with fin rays ; 21-41 

 oral cirri ; 23-29 pairs of gonads ; 

 oral sphincter vertically above 

 7th myotome. 



B. belcher i- -Average length 45 

 mm. ; myot. 62-66 ; average 

 formula 38, 17, 9 ; rostral fin 

 large. Other characters as in 

 B. lanceolatum. 



B. caribbceum — Average length 40 

 mm. ; myot. 59-61 ; average 

 formula 37, 15, 8; oral sphincter 

 over 5th myotome. Other 



characters as in B. lanceolatum. 



B. nakagawce — Average length 35 

 mm. ; myot. 62-66 ; average 

 formula 37, 17, 10, or 37, 16, 11 ; 

 Other characters as in B. lanceola- 

 tum. 



(b) Myotomes 69-79- 



B. calif orniense — Average length 

 74 mm. ; myotomes 69-73 ; aver- 



