Prof. F. 0. Guldberg on Movement in a Circle. 155 



XVI. — Description of a new Fish from Lake Nyassa. 

 By Gr. A. BOULENGEE, F.R.S. 



Chromis auratus. 



23 teeth on each side of the outer series of the upper jaw. 

 Depth of body 3f in total length, length of head 3^ times. 

 Profile of snout curved ; eye equally distant from the end of 

 the snout and the gill-opening, its diameter 4 times in length 

 of head and but slightly greater than interorbital width ; 

 maxillary not extending to below anterior border of eye ; 

 three series of scales on the cheek below the eye ; opercle and 

 interorbital region scaled ; prajopercular limbs forming a right 

 angle. Gill-rakers very short, 8 on lower part of anterior 

 arch. Dorsal XIX 6 ; spines subequal in length from the 

 fourth, which is ^ length of head. Pectoral pointed, f length 

 of head ; ventral as long as pectoral, reaching vent. Anal 

 111 6; third spine longest, stronger and a little longer than 

 dorsals. Caudal truncate. Caudal peduncle a little longer 

 than deep. Scales 34 j|, finely denticulate below the lateral 

 line I lat. 1. j^- Bright golden yellow, with three black stripes, 

 one along the side of the body from the eye to the base of the 

 caudal, a second above the upper lateral line from the occiput 

 to the caudal peduncle, and a third along the dorsal fin ; two 

 curved black bands across the snout from eye to eye ; a few 

 black spots on the upper part of the caudal fin. 



Total length 75 millim. 



A single specimen from Monkey Bay, W. Nyassa ; pre- 

 sented to the British Museum by G. 11. Pigott, Esq. 



XVII. — On Movement in a Circle as the Fundamerital Form 

 of Movement in Animals: its Cause, Manifestation^ and 

 ^Significance. By F. O. Guldberg *. 



[A Lecture t delivered before the Biological Society of Christiania, 

 March 30, 1896.] 



The majority of those who are accustomed to walk in the 

 fields and woods with open eyes for the observation of animal 



* Translated by E. E. Austen from the ' Biologisches Ceutralblatt,' 

 xvi. Bd., No. 21 (November 1, 189lj), pp. 779-783. 



t This lecture is a brief preliminary communication on the subject of 

 an investigation which, so long ago as the spring of the year 1888, the 



