13C NATURAL HISTORY OF ARCTIC AMERICA. 



ill the total, and about equals twice its owii length. Wliea exiianded, 

 tlie pectoral extends usually to the 7th dorsal spine (Gth to 8th). 



The distance of the ventral fioin the tip of snout sli}4htly exceeds A of 

 length of body. The length of the ventral spine is always a little less 

 than ^ of the length of the head. 



liadial formula.— D. IX-XI, 1, 10-11 ; A. 1, 9-11 ; C. +, IJ, + ; P. 10 ; 

 V. I, 1. 



Color. — General color dull silvery, minutely punctidated with black ; 

 upper half of body with large irregular areas of black ; chin, throat, and 

 abdomen black in males, silvery in the females studied. Nilsson records 

 a similar condition in O. punoitius.* 



The relations of Gastcroateus imngitim var. hraclujpodxi. to i\i(i pungitim 

 {=Pygosteus occidentaUs (C. & V.) Brevoort) of New England are shown 

 iu tlie table of comparative measurements w^hich follows. I do not use 

 the name PygoHtcus occidentalism for the reason that our many-spined 

 stickleback bearing that name shows no characters by which it may be 

 separated fi-om the Gastcrosteus pungitius of Linn(i as a species, and the 

 genus Pygosteus has nothing to exclude it fi-om Gasterosteus. The genus 

 Pygo.stciis, although credited to Brevoort, was not defined by him ; it 

 appears in Gill's Catalogue t as a name only. The first to indicate 

 characters by which it was thought the genus could be distinguished 

 was Jordan; they areCbtated to be the following : "Dorsal spines 7 or 

 more; sides mailed or not."| So far as the squamation is concerned, 

 tlie collections of the United States National Museum show all sorts of 

 individual variation, and justify the gronud taken by Giinther in his 

 arrangement of the varieties of G. aculeatus; certainly, the squamation 

 is not even of specific importance. The number of dorsal spines in the 

 specimens of G. pungitius studied ranges from 7 to 11. In Gasterosteus 

 inconstansj^ Kiitland, the range is fi'om 3 to 0. I have seen a iresh- 



*" Variat abdomine nigro."—FTO(l. Ichlh. Scand., 1832, p. 86. 



t Catalogue of the Pishes of the Eastern Coaat of North America fi'om Greenland to 

 Gi'orgia, by Theodore Gill, Jan. 1801, p. 39. 



t Maimal of the Vertebrates of the Northern United States, 1876, p. 248. 



$ Eucalia inoonsiam, Jordan, Manual of Vertebrates, 1876; Proc. Acad. Nat. Sci. Pliila., 

 1^7, p. Go. The generic characters ascribed to IJuralia are: (1) "Dorsal spiues iu a 

 right line," which is also true in Gasterosteus acuhaiufi, L. ; even in the many-spined 

 stickleback, G. jmngitius, I have frequently seen the last four or five spines in a right 

 lino, while the anterior ones preserved their zigzag aiTangement ; (2) " Ventral plates 

 coalesced into a narrow jdate on the mediau lino between the ventral fins," just as in 

 G. aculeatus and (;. j>uHgititu ; (3) "A distinct subMinadiate post-pectoral plate," which 

 is present in most sticklebacks ; the "associated characters "iudicati'd contain notiiing 

 generically distinctive. 



