94 Mathbun — American Species of PaUcus. 



C IVIeri without strongly dentate antei'ior crest. Lateral margin of 

 cai'apace with less tlian four teetli besides the orbital. 

 D. Antei'ior margin of meri of .second and third andjulatorj' legs 

 terndnating in a nearly rectangular non-projecting tooth. 

 E. Lateral teetli of carapai'c (k'litifurm, acute, scarcely projecting 

 Iieyoiid tiie margin of the carapace. zoiiatiiK Rathbun. 



E^. Lateral teeth tuberculiform or lobiforin, projecting from the 

 margin of the carapace. 

 F. Two frontal lobes, each bilolied. 



ulternalus Rathbun, new species. 

 F^. Two frontal lobes, each obscurely emarginate. 



isthinius Rathbun, new species. 

 D'. Anterior margin of meri of second and third ambulatory legs 

 terminating in a spiniform, jirojecting tooth. 

 E. Lateral margin of cara^iace with tiiree teeth besides the orbital. 



tuherculatus Faxon. 

 E''. Lateral margin with two teeth besides the orbital. 

 F. Branchial regions much swollen. 



obcsus A. Milne Edwards. 

 F''. Branchial regions not swollen. 



G. Granules of carapace very fine, not visible to the naked 

 eye. doitutus A. Milne Edwards. 



G^. Granules of carapace coarse. 



faxoni Rathbun, new species. 

 B'. Crests on the second and third abdominal segments and on the 

 fifth sternal segment forming conspicuous laminiform expansions 

 visible in a dorsal view. 

 C. Posterior margins of laminiform crests of first and second ab- 

 dominal segments subparallel in a dorsal view. 



huhameiisi!< Rathbun, new species. 

 C''. Posterior margins of laminiforui crests of first and second ab- 

 dominal segments not subparallel, that of the second having a 

 greater median expansion. 

 D. Ridge above the posterior margin of the carapace one unbroken 

 curve ; distal end of meri of ambulatory legs without a tooth. 



depressus Rathbun, new species. 

 D'. Ridge above the posterior margin sinuous ; distal end of meri 

 with a tooth. 

 E. Length of carapace more than f its width. 



angustus Rathbun, new species. 

 W. Length of carapace f its width or less. 



slcuA. Milne Edwards (restricted). 

 A''. Length of second ambulatory leg more than twice the width of the 

 carapace. 

 B. Front with two teeth. 



C. Chelipeds smooth. gntcilipes A. Milne Edwards. 



C^. Chelipeds tuberculate. aculifroiiH A. Milne Edwards. 



\y. Front with four tcotii. 



I 



