THE SPIDER CRABS OF AMERICA 



269 



H. coarctatus alutaceus has an extensive range. According to 

 Birula (1910) it reaches as far north and west as Bennett Island on 

 the Siberian coast, thence eastward to Bering Strait and southward 

 through the width of Bering Sea to Okhotsk Sea and the southern 

 shore of Sakhalin Island. Further south, Sea of Japan to Shanghai, 

 there is another well marked subspecies, Eyas coarctatus ursinus, 

 to be dealt with elsewhere. 



In the Arctic, alutaceus occurs also east of Bering Strait as far as 

 Point Barrow, Alaska, and again in 

 Beaufort Sea, Northwest Territories. 

 Although from this point to the Green- 

 land coast the species is absent, it is 

 the same form, alutaceus, which ap- 

 pears in lat. 70° 25' N., West Green- 

 land, and is continued thence south- 

 ward, by way of Hudson Strait and 

 Bay to Labrador, Newfoundland, and 

 Cape Breton. 



At Newfoundland and farther west 

 and south, that is, from Nova Scotia, 

 by way of Gulf of Maine, to North 

 Carolina, the form changes, but not 

 abruptly, into the typical coarctatus of 

 the British Isles. This form, follow- 

 ing the general direction of the Gulf 

 Stream, is continued northeasterly 

 from the Carolina coast to north- 

 western Europe; thence it extends 

 eastward in the Arctic only to the 

 Murman Sea and therefore fails to connect with the Siberian range of 

 alutaceus by nearly 100° of longitude. 



Besides the geographical variation there is much individual varia- 

 tion even in specimens from the same gathering, regardless of age or 

 sex. This makes the definite division into separate forms very diffi- 

 cult and unsatisfactory. Some of the variations are noted in the last 

 column of the distribution table. 



Measurements .—'LdiVgast specimen, male, examined (Grand Banks, 

 alutaceus, 40182), length of carapace 80, greatest width 64.5 mm. 

 Male (west Greenland), length 99, width 74 mm. (Hansen). Largest 

 American specimen, male, of typical form examined (off Cape Cod, 

 4555), length 30.2, width 19.7 mm. Largest specimen known of 

 typical form, male, Murman Sea, length 51.5, width 35 mm. (Birula, 

 1910). 



54S7— 2.5t 19 



Fig. 93.— Hyas coarctatus, male, carapace. 

 (After Smith, ms.) 



