24 Memoir Sears Foundation for Marine Research 



Range. Amphioxides larvae have been reported from localities so generally dis- 

 tributed and so widely separated*' that they are to be expected anywhere on the high seas, 

 within the latitudinal belt where Lancelets of the family Epigonichthyidae occur in any 

 abundance. 



Species. One specimen of Branchiostoma lanceolatum has been reported in the 

 Amfhioxides stage, i.e., it still retained its larval characters at a length of $•$ mm., al- 

 though this species usually undergoes its metamorphosis at about 4.5 mm." The other 

 Amphioxides larvae that have been described fall in two categories} the dorsal fin- ray 

 chambers of the one extend forward well beyond the first myotome, those of the other ter- 

 minate at the dorsal margin of the first myotome. Among the specimens of the second 

 group, some agree in number of myotomes with the Branchiostoma pelagicum of Gunther, 

 1889, and have been identified with the latter for this reason." Other specimens of the 

 group with a larger number of myotomes (70) for only two recorded specimens have been 

 described as a distinct species, Amphioxides stenurus Goldschmidt, 1905. But it is doubtful 

 whether the distinction between it and pelagicus is valid. The other category, with dorsal 

 fin-ray chambers extending far forward, has been named valdiviae Goldschmidt, 1905. 



None of these has been definitely connected with any particular parent species. In the 

 few specimens in which the rudiments of gonads were to be seen, however, these were in a 

 single series and on the left-hand side, suggesting an Epigonichthys or an Asymmetron 

 parentage; i.e., that they belong to the family Epigonichthyidae. 



Key to Species of Amphioxides 



la. Dorsal fin originates opposite 21st to 25th myotome; ventral fin about opposite 40th 

 myotome ; dorsal fin-ray chambers do not extend forward beyond dorsal edge of i st 

 myotome. 



2a. Not more than 68 myotomes. pelagicus Gunther, 1889, p. 25. 



2b. 70 myotomes. j/(?««r«j Goldschmidt, 1905. 



Indian Ocean, 

 lb. Dorsal fin originates opposite 32nd to 33rd myotome or even farther back; ventral fin 

 about opposite 43rd myotome; dorsal fin-ray chambers extend forward considerably 

 beyond dorsal edge of ist myotome. valdiviae Goldschmidt, 1 905, p. 27." 



48. Reported from the English Channel, Bermuda, off the Amazon and at several other localities in the equatorial 

 and south tropical Atlantic; mouth of the Red Sea; widespread in the tropical Indian Ocean; from the vicinity 

 of the Hawaiian Islands. For a distribution chart, to which might be added a few more recent records, see Gold- 

 schmidt (Dtsch. Sud-polar Exped., //, Zool. 3, 1909: pi. 11). 



49. Goldschmidt, Zool. Anz., 50, 1909: 443. 



50. So identified by Goldschmidt (Wiss. Ergebn. 'Valdivia,' 12, 1905: 46). But this identification cannot be re- 

 garded as final until the type specimen of Gunther's felagicum is re-examined, because his illustration of it 

 ("Challenger" Rep., Zool., j/ [2], 1889: pi. 6, fig. B) does not show the anterior termination of the fin-ray 

 chambers clearly. 



51. Previous accounts (Goldschmidt, Wiss. Ergebn. 'Valdivia,' j2, 1905: 46, pi. i, fig. 3, 4; Gibson, Trans. Linn. 

 Soc. Lond., Zool., [2] 75, 1910: 217, pi. 15, fig. i) base the distinction between valdiviae and pelagicus chiefly 

 on the shape of the tail fin, which is supposedly more sharply marked off and blunter at the tip, with the notochord 

 ending more bluntly in the former than in the latter. But the two supposed species appear to intergrade in this 

 respect. 



