236 Miscellaneoua. 



MISCELLANEOUS. 



The Bahama Amphioxus. By E. A. Andrews. 



In addition to the Amphioxus, or lancelet, found on the coasts of 

 many parts of Europe, some five others have been reported from 

 various parts of the world. Giinther recognizes these six as species 

 of Branchiostoma, that name having been given prior to the term 

 Amphioxus. The chief specific characters that can be made out 

 in the preserved specimens are the relative positions of anus and 

 atriopore as expressed by the number of muscle-segments anterior 

 to, between, and posterior to these openings. In addition to these 

 forms there is an undescribed lancelet in California, which, as far as 

 the above criteria may be trusted, belongs to a distinct species of 

 Branchiostoma, and a Japanese form that may prove to be one of the 

 known species. 



The great morphological interest attached to the lancelet as the 

 simplest and, in many respects, the most primitive of known verte- 

 brates makes the taxonomy and geographical distribution of this 

 group of more than common importance, and justifies a short pre- 

 liminary account of a new form found in the Bahamas. 



While the Johns Hopkins Marine Laboratory was stationed at 

 North Bimini, Bahamas, in the summer of 1892, many small lancelets 

 were taken swimming at or near the surface as well as living in the 

 calcareous sand on the flats exposed at low water. 



These partly pelagic acraniates diff'er so much from the known 

 forms that they may be regarded as generically distinct. Their chief 

 anatomical peculiarities are as follows : — 



(1) The gonads are developed^only upon the right side of the body, 

 both in the adult and in the young. 



(2) The notoehord, neural tube, and median fins are prolonged as 

 a considerable caudal process posteiior to the myotomes. 



(3) The ventral fin is without any fin-rays or successive fin-ray 

 chambers. 



(4) The pre-oral hood is extensive ; cirri smooth and united by 

 the hood-membrane for the greater part of their length. 



(5) The right metapleuron is continuous with the median ventral 

 fin, which passes to the right of the anus. 



(6) The "olfactory pit" is apparently absent. 



(7) Myotomes anterior to atriopore 44, between atriopore and 

 anus 9, posterior to anus 13 : total 66. Length 13-16 millim. 



(8) Swims free in the evening both at Bimini and in Nassau 

 Harbour. Lives also in the calcareous sand. 



An illusti'ated description of these characters of this new genus 

 of acraniates will appear in a forthcoming number of vol. v. of the 

 *■ Studies from the Biological Laboratory.' — Johns Hopkins Universitif 

 Circulars, vol. xii. no. 106, p. 104. 



