Fishes of the Western North Atlantic ii 



Branchiostoma bermudae Hubbs, 1922 

 Figure 2 A-D 



Study Material. Nineteen specimens, 29 to 49 mm. long, from Bermuda (U. S. Nat. 

 Mus. and Harv. Mus. Comp. Zool.). 



Distinctive Characters. Among Atlantic species, B. bermudae differs noticeably from 

 B. lanceolatum and from B. ajricae in that its anus is about opposite the midpoint of the 

 lower lobe of its caudal fin. In this respect it closely resembles B. flatae and B. caribaeum, 

 but it is separable from both of these by a smaller number of myotomes ( 56 at most) as well 

 as by generally fewer precaudal fin-ray chambers (9 to 24, usually less than 16). The 

 average number of dorsal fin-ray chambers also is smaller. 



Additional Description. Anterior end of notochord extending forward in rostrum in 

 a straight line; rostral fin marked off from dorsal fin by a subtriangular notch; origin of 

 lower lobe of caudal fin anterior to origin of its upper lobe by a distance about ^/-j, as great 

 as length of lower lobe; dorsal fin % to /^ as high as distance from its base to margin of 

 metapleura in the midregion of body; anus a little behind the midpoint of lower lobe of 

 caudal fin; origin of lower caudal lobe about midway between its tip and atriopore; dis- 

 tance from tip of caudal to anus about 0.4 of distance from anus to atriopore; dorsal fin-ray 

 chambers 204 to 242, the highest 3 to 4 times as high as long; precaudal fin-ray chambers 

 9 to 24; 35 or 36 myotomes anterior to atriopore; 12 to 14 between atriopore and anus, 

 5 to 7 posterior to anus, total number 54 to $6; gonads, 22 to 28 pairs. 



Color. Living specimens are semitransparent and iridescent, but they become opaque 

 after preservation. 



Size. Maximum recorded length, 53.5 mm."' 



Habits. The Bermuda Lancelets are usually found in one-half to six fathoms of water 

 on coarse sandy bottom into which they burrow tail first and there remain most of the time 

 with only the anterior part of the body exposed. If disturbed they swim vigorously for a 

 short time but soon return to the sand. Observations in aquaria have shown that normally 

 they are no more active by night than by day. Under experimental conditions they usually 

 swim with the anterior end foremost. If a stimulus is applied to the anterior end, the 

 Lancelet may dart backward for a short distance, or it may turn end for end. But this 

 reversal in direction is of short duration, for it soon turns again and proceeds at only a 

 slight angle from its original course. In taking to bottom after swimming, Lancelets usu- 

 ally sink quietly through the water to the sand; when in contact with the latter they may 

 either lie there, passive for some time; or they burrow at once, usually tail first, or head 

 first on rare occasions. When buried they usually are tortuous in outline, probably from 

 being crowded among the grains of sand." 



Specimens adapted to the summer temperatures of Bermuda (about 31° C.) dart 



2 1. Hubbs, Occ. Pap. Mus. Zool. Univ. Mich., 105, 1922: 10. 



22. For detailed accounts of the experiments on which the above is based, see Arey (J. exp. Zool., 29 [i], 1915 : 37) 

 and Parker (Proc. Ainer. Acad. Arts Sci., ^3 [16], 1908: 413). 



