THE CANCROID CRABS OF AMERICA 177 



ing the inner angles of the orbit. Eyestalks short; orbits small, with 

 two jBssures in both upper and lower margins. Basal article of an- 

 tenna usually somewhat enlarged and united with the front, thus 

 excluding the flagellum from the orbit. 



KEY TO THE AMERICAN SPECIES OF THE GENUS CANCER 



A'. Antero-lateral and postero-lateral margins meeting at a distinct angle. 

 Lateral teeth 9, 10 or 11; carapace widest at ninth or tenth (sometimes 

 eighth) tooth. 

 B'. Branchial regions not nearly meeting on median line. 



CK Front between the eyes markedly produced beyond outer orbital 

 angles and formed of 5 subequal teeth. Fingers of chelipeds dark- 

 tipped productus, p. 203. 



C^. Front between the eyes not markedly produced beyond outer orbital 

 angles and formed of 5 unequal teeth. 

 Di. Antero-lateral teeth 10, carapace widest at tenth tooth. Postero- 

 lateral margin of carapace unbroken, entire. Fingers without 



dark color magister, p. 222. 



D^. Antero-lateral teeth 9, carapace widest at ninth (sometimes 



eighth) tooth. Postero-lateral margin of carapace with one, 



two or three small teeth or notches. 



E'. Antero-lateral margin of merus of outer maxilliped arcuate. 



First 8 antero-lateral teeth of carapace projecting less 



than one-third the width of base, not spiny-pointed. 



Fingers without dark color gracilis, p. 219, 



E^. Anterior and outer margins of merus of outer maxilliped 



nearly straight and meeting at a blunt angle. (Maxilliped 



of luederwaldti not known.) 



F'. Fingers wholly light colored. Carapace coarsely 



granulate. 



Qi. Edge of antero-lateral teeth entire. Cheliped? 



granulate, not denticulate irroratus, p. 180. 



G^. Edge of antero-lateral teeth denticulate. Upper 



margin of palm denticulate borealis, p. 182. 



F2. Fingers partially or almost entirely dark colored. 



G'. Antero-lateral teeth dentiform, more or less pro- 

 jecting. 

 HI. Antero-lateral teeth not prominent, projecting 

 at the utmost scarcely more than half the 

 width at base. 

 J^ Carapace slightly uneven. Edges of lat- 

 eral teeth denticulate. Median tooth 

 of front very narrow, subacute. 



anthonyi, p. 218. 

 J2. Carapace very uneven especially in female. 

 Edges of lateral teeth entire. Median 

 tooth of front blunt or subtruncate. 



amphioetus, p. 205. 



H2, Antero-lateral teeth prominent, projecting from 



a half to two-thirds or more of the width at 



base; teeth sharp-pointed, hooked forward, 



posterior margins convex, anterior concave. 



79856—30—13 



