ORDER DECAPODA — PLATYONICHUS. 9 



Color, deep bottle-green behind, where it is spotted with brown ; sea-green in front. Be- 

 neath, in young individuals, light sea-green ; in the adult, tinged with indian red. Body and 

 feet with distant minute spots, arranged on the feet in more or less distinct series. 



Length, 1*0- 1*5. Transverse diameter, 1*3-1 '8. 



This Crab is so insignificant in its economical uses, that it has received no popular name. 

 It occurs abundantly along the rocky shores of Long island sound, among seaweed. At 

 Newport, it is of a larger size, and it appears to become larger northwardly. The C. 

 granulatus of Say is passed over in silence in the latest and best treatise on these animals 

 by Edwards, but we have no doubt that it is identical with the C. momas or common edible 

 crab of Europe. 



GENUS PLATYONICHUS. Latreille. 



Shield nearly orbicular. Front narrow and toothed. The external antennae of three joints, 

 the first of which is not firmly united to the front, but movable. Second pair of tarsi 

 somewhat flattened, lanceolate ; the others acute ; the posterior pair oval, and adapted for 

 swimming. 



PLATYONICHUS OCELLATUS. 



PLATE I. FIG. I ; AND PLATE V. FIG. 7. 



Cancer ocellatus. Herbst, Versuch u. s. w. pi. 49, fig. 4. 



Platyonichus id. Latreille, Encyclopedic, Vol. 16, p. 152. 



Porlunus pictus. Say, Jour. Acad. Nat. Sciences, Vol. !, p. 62, pi. 4, fig. 4. 



Platyonichus oceUatus. Milne-Edwards, Hist. Nat. des Crustaces, Vol.1, p. 437. 



P. id. Gould, Invertebrata of Massachusetts, p. 324. 



Description. Shield and anterior pair of feet minutely granulate. Front and antero-lateral 

 border with stout spines ; five on each side of the shield, including the orbital spines, and one 

 on the front beside the two formed by the inner angle of the orbits. A narrow fissure in the 

 orbits above, and a long oblique spine beneath and internally. Third joint of the external 

 pedipalpi deeply emarginate on its inner side, and elongate and rounded at the tip. Terminal 

 joint of the abdomen very small, pentagonal. Second pair of feet not as long as the first, but 

 longer than the others ; the penultimate joint of the third and fourth with two impressed lines 

 on the posterior, and one on the anterior smrface. The tarsus of the second more compressed 

 and broader than the first and third ; the posterior tarsi oval. Hands large, subequal ; the 

 arm extending greatly beyond the margin of the shield, and three-spined on its inner edge. 

 Carpus trigonal, with two spines, of which the internal is longest and most acute. Hand 

 with the outer margin strongly carinate and tubercular ; the inner ciliate, and with an acute 

 spine at the inner tip. Thumb trigonal, depressed, with prominent edges, hooked at the tip 

 with from ten to fifteen unequal tubercular prominences : finger straight, somewhat exceeding 

 the thumb, and hooked at the tip. Series of long hairs on the shell, beneath the antero-lateral 



Fauna — Part 6*. 2 



