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CRUSTACEA. 
Genus Cancer, (Leach, and Bell,) (Platycarcinus, 
Latr. and Edw.) 
C. productus. Mus. Acad. 
Testa depressa ; fronte subquadrata, valde producta, ob- 
tusfe 5-lobata, lateribas 9 vel 10-lobatis. 
Shell greatly flattened behind the front, and an- 
tero-laterally ; front greatly produced beyond the 
orbits, terminating in five nearly equal and not very 
distinct lobes, the middle lobes not greatly produced 
beyond the lateral ones; antero-lateral margin of 
the carapax with nine or ten nearly equal, obtuse, 
lobe-like teeth, postero-lateral margin very concave; 
anterior feet tuberculous above ; pincers very short. 
One specimen, brought by Mr. Nuttall from 
West America. 
Length hardly one inch, but probably attains a 
greater size. 
C. irroratus , (Say.) Mus. Acad. 
Two specimens, brought from West America by 
Mr. Nuttall; not essentially differing from those 
found on the coast of New England. 
This species is so liable to vary with age, both in 
the thoracic markings and in the shape and direc- 
tion of the marginal teeth, that without care one 
might easily mistake varieties for distinct species. 
M. Edwards states that the frontal teeth in this 
genus form an uneven number, one always growing 
