PORTUMNUS. 
CANCER latipes, Planci, 
CANCER, Pennant. 
PORTUMNUS, Leach. 
Antemee externce setacem articulis duobus primis majoribus, in oculorum cantho interuo inserts. 
Pedipalpi gemini externi caulis interni articulo secundo ad latus iuternum emarginato pro inser- 
tione palpi triarticulati, elongato-subconici. 
Pedum par anticum majus, a?quale didactylum ; paria 2, I, et 4 compressa unguibus compressis, 
sulcatis interneque basin versus dilatatis instruct a; par quintum compressum ungue 
foliaceo, sublanceolato. 
Abdomen Maris 5-articulatum articulis tertio longiore, quarto elongato * : Femince 7-articula- 
tum articulo ultimo prscedente haud abrupte angustiore. 
Tester margo anticus arcuatus, semicircularis lateribus sensim postice in angulum conver- 
gentibus, apice subtruncato; diametro longitudinal i transversum squante; orbita integra, 
angulo interno imperfecto. 
Oculi pedunculo mediocri baud crassiores. 
External antennae setaceous, with the two first segments largest, inserted at the internal 
corner of the eve. Second joint of the internal footstalk of the external double palpes with the 
internal side notched for the insertion of the elongate-conic palpes, which arc composed of three 
joints. Anterior pair of legs largest, didactyle, and equal in size; second, third, and fourth 
pairs compressed, furnished with compressed, longitudinally grooved claws, which are dilated 
internally towards their base; fifth pair compressed with a foliaceous somewhat-lanceolate claw. 
Abdomen of the male five-jointed, the third segment longest, the fourth elongate; of the female 
seven-jointed, the last segment not abruptly narrower than the sixth. Anterior margin of the 
shell semicircular, with the sides gradually converging to an angle behind; the apex truncate; 
the transverse diameter not exceeding the longitudinal ; orbit entire, with the internal angle 
imperfect. Eyes not thicker than their footstalk, which is short. 
The genus Portumnus is distinguished from Portunus by having equal sized fore legs; by 
having all the claws compressed; by the proportion of the first joint ot the abdomen in the male, 
and the seventh in the female; by the form of the shell ; the entire orbits, and more slender eyes. 
From the more compressed form of the legs it has doubtless a much greater facility of swimming 
in the ocean. 
* In Carcinis, Portunk transverse. 
