Fishes of the Western North Atlantic 453 



A. The acanthias group: ist dorsal spine over or behind the inner corner of the pec- 

 toral; midpoint of bases of pelvics much closer to 2nd dorsal than to ist; distal margin of 

 pectoral at least moderately concave; anterior margin of nostril simple (not bilobed); 

 at least most of the members of the acanthias group are white-spotted, while the others 

 are not. 



B. The blainville-jernandinus group: ist dorsal spine almost over midpoint of 

 inner margin of pectoral ; midpoint of bases of pelvics about midway between the two dor- 

 sal fins; inner margin of pectoral nearly straight; anterior margin of nostril bilobed (Fig. 

 87E,F). 



C. The brevirostris-cubensis group resembles the blainville-jernandinus group in 

 relative position of fins and in bilobed nasal margin, but is set apart by the distal margin of 

 the pectoral, which is deeply concave with its inner angle noticeably acute. 



Group A is represented in the North Atlantic by the familiar Spiny or Piked Dog- 

 fish {S. acanthias) of temperate and boreal latitudes. A close relative in the North Pacific 

 is usually regarded as specifically distinct {suckleyi Girard) but recently has been listed 

 as acanthias. ^^ According to recent Keys'" the chief alternative character supposedly sepa- 

 rating suckleyi from acanthias is the position of the first dorsal spine, opposite or a little 

 behind the inner corner of the pectoral in the former, behind and remote from it in 

 the latter. Actually, however, our Study Material shows that this criterion is not tenable; 

 not only is the variation considerable in this respect among both Atlantic and Pacific speci- 

 mens, but in some of the latter the first dorsal spine stands as far behind the pectoral as it 

 does in any of the Atlantic series.'' It is even doubtful whether there is any average dif- 

 ference between the two populations in this respect. Nor have we been able to find any 

 other difference to separate them, whether in position of fins, in proportionate dimensions, 

 or in teeth. In short, the North Pacific and North Atlantic populations of the acanthias 

 group have not differentiated themselves specifically during the period since their ranges 

 became discontinuous. 



It is doubtful whether this group occurs in the equatorial Atlantic, unless accidentally. 

 But it is as widespread in the temperate and boreal belts of the southern as of the northern 

 hemisphere. Thus the Spiny Dogs of the Straits of Magellan," Australia and New Zea- 

 land,"* with those reported from Uruguay and northern Argentina as Squalus acanthias''' 



11. Soldatov and Lindberg, Bull. Pacif. Fish. Res. Sta., 5, 1930: 16; eastern Asia. 



12. Garman, Mem. Harv. Mus. comp. Zool., 56, 1913: 192; Fowler, Bull. U.S. nat. Mus., 100 (/j), 1941: 257. 



13. Especially significant is the fact that among three embryos of a single brood from San Francisco the first dorsal 

 spine occupies the same position relative to the pectoral as is commonly true in Atlantic specimens; in another 

 one it is as usually stated for the Pacific form. 



14. A. lebruiii Vaillant, Miss. Sci. Cape Horn (1882-83), 1885: 13, pi. i. 



15. Fernandinus Waite (Rec. Canterbury [N. Z.] Mus., i, 1901: 14.2, pi. 16, fig. i) appears to be identical with 

 kirki Phillipps (N. Z. J. Sci. Tech., 12, 1931 : 361) from New Zealand, and with whitleyi Phillipps (N. Zealand 

 J. Sci. Tech., 12, 193 i : 361) from South Australia. It is true that the illustration (McCoy, Prod. Zool. Victoria, 

 1886: pi. 75, fig. lb) on which w/titUyi was based fails to show any labial furrows, but this was probably an 

 oversight, for McCoy not only includes labial furrows in the generic diagnosis but states that he %vas unable to 

 detect any difference between Australian and British specimens. 



16. Berg, An. Mus. nac. B. .\ircs, (2) /, 1895: 6; Devincenzi, An. Mus. Hist. nat. Montevideo, (2) /, 1920: 123; 

 Lahille, Physis B. Aires, 5, 1921 : 63. 



