Number 94 January 22, 192 1 



OCCASIONAL PAPERS OF THE MUSEUM OF 

 ZOOLOGY 



UNIVERSITY OF MICHIGAN 



Ann Arbor, Michigan Published by the University 



THE LATITUDINAL VARIATION IN THE 

 NUMBER OF VERTICAL FIN-RAYS 



IN LEPTOCOTTUS ARMATUS 



By Carl L. Hubbs 



It has frequently been noted that the number of vertebrae 

 and related characters of fishes, the fin-rays included, increase from 

 tropical waters toward the poles — a problem now being investi- 

 gated from several angles by the present writer. This short paper 

 is presented as an addition to the data bearing on the phenomenon. 



It has already been observed by Nichols' and by Starks (MS) 

 that the dorsal and anal rays of Leptocottus armalus tend to increase 

 in number toward the north, but neither of these ichthyologists 

 possessed sufficient material from the critical region of the south- 

 central coast of California; a deficiency overcome by the writer, 

 who collected extensively in this region in 1916. The sharpest 

 break in the series occurs in central California, enabhng the 

 distinction of a southern comparatively few-rayed subspecies from 

 a northern many-rayed form; this break conforms with a like 



^ Proc. Biol. Soc. Wash., XXI (190S), 172. 



