A EE VISION OF THE BEANCHIOSTOMID^. 319 



Maximum length observed in 12 specimens 1*9 cm. 

 (J. W. K.). 



Distribution. — Off the Bahamas, pelagic (?). 



E-emarks. — Several interesting points in the structure of 

 this species are detailed in Mr. Andrews' account (loc. cit.). 

 Attention may especially be drawn to the following in addition 

 to those which have been indicated as generic and specific 

 characters. The anus occupies a nearly median position, the 

 ventral fin being here deflected to the right, occupying thus 

 more nearly its true morphological position as right metapleur. 

 The first pair of nerves arise below the eye-spot; in place of the 

 second pair there is a single nerve, which, with the first pair, 

 supplies the rostrum. 



In young specimens the urostyle-like process is not developed, 

 and there is a terminal caudal fin. 



The terminal branches of the rostral nerves are furnished in 

 all Brauchiostomidse with cellular end-organs; these are of 

 especially large size in A. Lucayanum. 



Incertae Sedis. 

 1. AMPmoxus ELONGATUs, Suudevall. 'Ofvers. vet. Akad. Forhand.,' 



1852, p. 147. 

 Branchiostoma elongatum, Sundevall. ' Ofvers. vet. Akad. For- 



baud.,' 1853, p. 12. 



Myotomes 79. Formula 49, 18, 12. Dorsal fin low. Caudal 

 fin small. Oral cirrhi wanting. No eye-spot. Length 6 cm. 



Distribution. — Coast of Peru. 



Remarks. — This species is described as above by Sundevall, 

 but the description does not enable us to determine whether 

 the species belongs to the sub-genus Amphioxus or Hetero- 

 pleuron, or to the genus Asymmetron, or to a distinct genus. 

 The apparent absence of oral tentacles is very probably due to 

 alcoholic shrinking. 



Eigenmann (3) records the capture of a number of Branchio- 

 stoma from San Diego Bay, California, which he is disposed 

 to refer to this species, but from his description it appears 

 probable that they belong to the species A. californiensis. 



