Fishes of the Western North Atlantic 9 



Species. The characters that have been used chiefly in the classification of the species 

 of the genus are: (i) number of ventral fin-ray chambers; (2) number of dorsal fin-ray 

 chambers; (3) height of dorsal fin in relation to height from its crest to the margins of 

 metapleura; (4) shape of caudal fin; (5) location of anus in lower lobe of caudal fin; (6) 

 number of preatrial myotomes; (7) total number of myotomes. The five species that have 

 been described from the western Atlantic {B. caribaeum Sundevall, 1853; ^- bennudae, 

 B. floridae, B. platae and B. virginae Hubbs, 1922) with the anus near, or posterior to, the 

 midpoint of the ventral lobe of the caudal fin differ sharply from B. lanceolatiim and 

 B. ajricae of the eastern Atlantic, in which it is considerably farther anterior to it. Among 

 this western Atlantic group, B. bermudae and B. platae are set apart by the fact that the 

 lower lobe of the caudal fin originates considerably anterior to the origin of its upper lobe 

 (Fig. 2 A, F), whereas in the others the two lobes originate opposite one another. B. ber- 

 mudae is sharply separated from B. platae by a considerably smaller number of dorsal fin- 

 ray chambers (200-242 vs. 278-330), and fev/er myotomes (not more than 56 vs. at 

 least 58). But B. fioridae and B. virginae agree with B. caribaeum in the position of the 

 anus, while counts of fin-ray chambers and myotomes in the specimens we have studied 

 (Study Material, p. 13), together with those previously published, fail to show any clear 

 distinctions among the populations of Virginia, North Carolina, Florida (including the 

 Tortugas) or Porto Rico (representing the West Indian region). The most that can be 

 said is that some Florida and West Indian specimens have fewer precaudal fin-ray cham- 

 bers than have yet been recorded for more northerly localities. But this is not always true, 

 since the maximum recorded counts are in fact for one specimen from Florida and for one 

 from North Carolina. Therefore it cannot be invoked as a basis for specific separation. 



Key to Species of Branchiostonia 



la. Caudal fin hardly higher than dorsal and ventral fins. w/«M^^«iirt Whitley, 1932. 



Queensland. 

 lb. Dorsal or ventral lobe of caudal fin, or both, considerably higher than dorsal and ven- 

 tral fins. 

 2a. Caudal fin not clearly marked off from ventral fin. capense Gilchrist, 1 902. 



South Africa. 



2b. Caudal fin clearly marked off from ventral fin. 

 3a. Anus about at point of origin of caudal fin. 



4a. Distance from anus to tip of caudal fin only Y-> distance from anus to 

 atriopore. bazarutense Gilchrist, 1923. 



East Africa. 



4b. Distance from anus to tip of caudal fin about as great as from anus to 

 atriopore. haeckeli Vvd^nz, i<)iz. 



Ceylon. 



3b. Anus clearly posterior to origin of caudal fin. 



