THE SPIDER CRABS OF AMERICA 235 



Bering Strait to the Aleutian Islands and to Korea (lat. 36° 01' 30" 

 N.). Littoral to 350 fathoms (West Greenland) and 1,215 fathoms 

 (Sea of Japan). Chile (Streets). 



Variation. — Varies as to roughness of carapace, amount of hairiness 

 and length and \\-idth of legs, especially of the merus. In the Sea of 

 Japan the legs are longer than elsewhere, the merus of the second leg 

 usually exceeding that of the first in old males; the length of the 

 second merus is from 5.5 to 6.3 times its width. The same article in 

 similar specimens from Greenland and the Atlantic has a length of 

 from 4.9 to 5.2 times its width, and is shorter or just as long as the 

 first merus. The typical form of the species reappears in Alaskan 

 waters and Bering Sea, but in the Okhotsk Sea there is a tendency 

 toward the long-legged form of the Sea of Japan. This form may be 

 known as Chionoecetes opilio elongatus. (See table.) 



Material examined. — See table, pages 236-242. 



CHIONOECETES BAIRDI '^ Rathbun 



Plates 86 and 87 



Chionoecetes opilio Rathbun (part), Proc. U. S. Nat. Mus., vol. 16, 1893, 



p. 74. 

 Chionoecetes hairdi Rathbun, Proc. U. S. Nat. Mus., vol. 64, art. 14, 1924, 



p. 3 (type-locality, head of Kingcombe Inlet, British Columbia; H. E. 



Nichols; 1 male, holotype, Cat. No. 5862, U.S.N. M.). 



Diagnosis. — Near opilio. Carapace a little wider than long (length 

 measured to tip of rostral teeth) . The spines in the row leading from 

 the pterygostomian region backward to the branchial region become 

 suddenly larger, the last three or four spines being of considerable 

 size; in opilio these spines do not increase notably in size. Several 

 other prominences of the antero-lateral regions are spinous instead 

 of tuberculous. Outer orbital tooth curved more strongly inward 

 than in opilio, rostral teeth narrower, interspace wider. Spines of 

 legs longer. 



Description. — ^The branchial regions are more depressed than in 

 opilio, and in consequence the width is greater; the width exceeds the 

 length, while in opilio the width is subequal to the length. The inclined 

 subtriangular facet of the anterior branchial region is steeper, higher 

 and shorter than in opilio; the highest point is marked b}' a spine, 

 instead of a tubercle; in opilio, there are no dorsal spines, that is, none 

 above those in the submarginal row. In hairdi the last (posterior) 

 three or four spines of the pterygostomian-branchial row are notably 

 enlarged; also the outermost of the prominences in the transverse 

 branchial row is spinous or spinulous. The whole animal is rougher 

 than in opilio. The carapace is narrower across the orbits, the outer 

 orbital teeth are bent inward more; the median emargination of the 

 front is wider and the teeth narrower and with less arched margins, 



" For Prof. Spencer F. Baird, first U. S. Comniissioner of Fish and Fisheries. 



