400 REPORT OF THE COMMISSIONER OF FISHERIES. 



e\ Intramedial region narrow, its anterior width about two times its length. 

 /. Verges greatly exceeding the third segment of the abdomen. 



g. Tips of verges straiglit. Second to sixth antero-lateral teeth eciui- 



lateral C. dana'. 



(/. Tips of verges curved. Antero-lateral teeth -with jiosterior margins 



longer than anterior C. arcuatus. 



p. Verges exceeding the third segment but little, or not at all. . C. larvatus. 



cP Lateral sjiine less than twice the length of preceding tooth C. cxasperatus. 



c^. Verges reaching the extremity of the abdomen or nearly so. 



d. Antero-lateral region granulate. Lateral spine between two and three times 



length of preceding tooth C. to.rotes. 



d\ Antero-lateral region smooth. Lateral spine less than twice the length of 



preceding tooth C. bocourti. 



rt\ Inner supraorbital fissure open C. heUlcosus. 



Toward the southern half of its range the true C. sajjidus is more 

 or less replaced locally' by a varietal form, C. sapldus acutideus Rath- 

 bun, which differs in the possession of an accessor}^ tooth on the inner 

 margin of each of the pair of median frontal teeth. This form begins 

 to appear in the Gulf of ^Mexico and is apparently common on the 

 coast of Cuba and probabl}' other of the West Indian Islands. 



DISTRIBUTION ANL> HABITAT. 



The natural range of the blue crab is from Massachusetts Ba}^ to 

 some as yet undetermined point on the east coast of South America. 

 On the coast of the United States it is common from Cape Cod to the 

 southern extremity of Texas, and throughout the greater portion of 

 this long coast line it is ver}' abundant. Its favorite habitat is in the 

 waters of some bay or at the mouth of a river, and it seems to prefer 

 shallow water to that of much depth. Consecpiently, such bodies of 

 water as Delaware Bay, Chesapeake Bay, and the protected channels 

 along the coasts of Virginia and other South Atlantic and Gulf States 

 fairly swarm with these creatures. Chesapeake. Bay is especially fav- 

 orable and has long been famous, not only for the great number of 

 crabs which it produces, but also for their large size and exceptionally 

 fine flavor. 



Although the blue crab is essentially an inhabitant of salt water, it 

 is frequentl}^ found in water that is only slightly brackish or even 

 apparently quite fresh. Specimens have been recorded from the Hud- 

 son River as far north as Newberg and on credible authority I have 

 learned of the presence of an occasional individual in the Potomac 

 River and the Eastern Branch opposite the cit}- of Washington. At 

 Crisfield, Md., and at other points along both the eastern and western 

 shores of Chesapeake Bay, I have frequently observed the blue crab 

 in ponds and ditches, often at a distance of a mile or two from the bay 

 and in water that was nearly fresh. In such situations it was often 

 living in shallow burrows in the banks, but I was unable to determine 

 whether these were of its own construction. 



