42 S. I. Smith — Crustaceans of the Atlantic Coast. 



ences in tlie proportional lengths of the first and second pairs of legs, 

 referred to by Stinipson, are variations dne wholly to age and sex. 

 The proportions given by Kroyer apply well to large males, like the 

 specimen represented in his figure above referred to, while those 

 given by Stimpson apply to specimens of smaller size. The following 

 measurements exhibit these variations and show that they are even 

 much greater in very young specimens than indicated by Stimpson. 

 The proportions of the carapax in the specimen from Casco Bay [h] 

 may have changed slightly by contraction in drying after partial 

 digestion in a fish-stomach. 



Length of carapax, 



Breadth of carapax, 



Ratio of length to breadth, 



Between external angles of orbits, 



Length of chehped. 



Length of anterior ambulatory leg. 



Length of carapax, 



Breadth of carapax, 



Ratio of length to breadth. 



Between external angles of orbits, 



Length of cheliped, 



Length of anterior ambulatory leg. 



Upon the N^ew England coast this species is very rare and appar- 

 ently confined to deep water and to the off-shore banks. It is one of 

 the largest arctic crabs and occasionally attains gigantic proportions. 

 The extent of the ambulatory legs, in the largest individual referred 

 to above, was about 800 millimeters (over two and a half feet), while 

 the specimen figured by Kroyer was even somewhat larger. 



I have not been able to consult Otho Fabricius' original descrip- 

 tion of Cancer opilio, referred to by Kroyer, nor even to ascertain 

 with certainty the exact date of its publication, which was very likely 

 subsequent to that of Cancer opilio of J. C. Fabricius (Entomologia 

 systematica, ii, p. 458, 1793), which is I?iachus opilio of the same 

 author (Supplementum entom. system., p. 356, 1798) and the Pisa 

 armata of Milne-Edwards. Even if priority of publication belongs 

 to the species of J. C. Fabricius, I should not regard such a preoccu- 

 pation in the ancient genus Cancer as suflScient reason for rejecting 

 a name so well-established as opilio for the species under discussion. 

 I see far less reason for restoring the old name phalangium which 

 had not been in use for this species for more tlian three quarters of a 



