232 BULLETIN 12i9^ UNITED STATES NATIONAL MUSEUM 



fathoms; S. brk. Sh.; station 2764; 10 young (21907). Lat. 36° 43' 

 00" S.; long. 56° 23' 00" W.; 103^ fathoms; S. brk. Sh.; station 

 2765; 25 young (21908). Lat. 36° 47' 00" S.; long. 56° 23' 00" W.; 

 103^ fathoms; S. brk. Sh.; station 2766; 4 young (21909). 



Genus CHIONOECETES Kroyer 



Chionoecetes Kroyer, Natiirh. Tidssk., ser. 1, vol. 2, 1838, p. 249; type, 

 C. opilio (O. Fabricius). 



Peloplastus Gerstacker, Arch. f. Natiirg., vol. 22, pt. 1, 1856, p. 102, pub- 

 lished April, 1857, according to Stimpson; type, P. pallasii Gerstacker == 

 C. opilio (O. Fabricius). 



Carapace about as broad as long, breadth at orbits about half as 

 great as across branchial regions; either depressed or partially in- 

 flated, more or less tuberculate or spinose. Rostrum short, divided 

 into two flat, triangular horns. Orbits large, shallow, open above 

 so that the short, thick eye-peduncles are visible from above when 

 retracted; cornea large. No preocular tooth or spine; a large post- 

 ocular tooth, directed forward. Basal antennal article narrow, 

 diminishing distally and ending in a spine; next two articles not 

 dilated; flagellum short. 



Chelipeds much shorter than the first three ambulatory legs; 

 fingers long and narrow; palm only slightl}^ enlarged until the crab 

 reaches considerable size (100 mm. or more). Legs more or less 

 compressed. Abdomen composed of seven segments. 



Occurs from Cortes Bank (lat. 32° 17' 00" N.), off San Diego, 

 California, northward through Bering Sea and Strait to the Arctic, 

 westward on the Siberian coast to long. 173° 24' 00" W. and eastward 

 on the Alaskan coast as far as a point 10 miles west of Point Franklin. 

 West coast of Greenland (lat. 70° 42' 00" N.) southward to Casco 

 Bay, Maine. Kamchatka; Okhotsk Sea to south coast of Hokkaido 

 (Jesso); sea of Japan to lat. 36° 01' 30" N. (coast of Korea). Chile. 

 Littoral to 1,625 fathoms. 



KEY TO THE SPECIES OF THE GENUS CHIONOECETES 



A'. Branchial regions depressed or slightly swollen. Lateral margin of carapace 



exposed in dorsal view as far forward as first pair of ambulatory legs. 



Rostrum horizontal. Meropodites of legs broadly dilated. 



B'. Length and breadth of carapace subequal; dorsal surface ornamented with 



tubercles. Spines of pterygostomian-branchial row small, numerous, 



and of nearly equal size opilio, p. 233. 



B^. Carapace broader than long; dorsal surface with a few spines anteriorly. Last 



three or four spines of pterygostomian-branchial row large bairdi, p. 235. 



A^. Branchial regions much swollen dorsall}- and laterally concealing a large part 



of the side margins of the carapace. Dorsal surface spinous. Rostrum 



ascending. Meropodites of legs narrow. 



B'. The two dorsal branchial ridges meet outwardly in a curved line marked 



by two subequal spines. Posterior marginal arch of carapace medially 



interrupted. Interbranchial space very deeply depressed. 



tanneri, p. 243. 



