198 CRUSTACEA. 



foot-jaws are foliaceous. It is of a red colour, and was discovered by 

 Sir Joseph Banks in his voyage round the world. It collected in 

 such immense numbers that the Ocean seemed to be of one blood-red 

 colour. 



The Mglea, Id., is only distinguished from the preceding genus, 

 and from Galathea, by the dentation of the mandibles, by the second 

 joint of the external foot-jaws being shorter than the first, and by the. 

 surface of the body being generally smooth *. 



That which Risso first named CALYPSO, and subsequently JANIRA, 

 in the opinion of Desmarest, Consider., p. 192, does not differ from 

 Galathea. 



PORCELLANA, Lam. 



The Porcellanae form a singular exception among the Macroura, 

 with respect to their tail, which is doubled under as in the Brachyura. 

 They are otherwise removed from the Galatheue by the more ab- 

 breviated, suborbic-ular, or almost square form of their thorax ; by 

 the mediate antennae, which are sunk in their fossulye, by their tri- 

 angular forceps ; and finally, by the internal dilatation of the inferior 

 joints of their external foot-jaws. Their body is very flat. 



They are small, slowly-moving Crustacea, found in every sea, 

 and conceal themselves under stones near the shore. 



Doctor Leach has formed a genus with certain species hexapus 

 Latr., longicornis, Id., Bluteli, Risso, Crust., I, 7, &c., which he 

 calls PISIDIA. According to Desmarest, however, it does not differ 

 in any appreciable character. 



Some of them are remarkable for their extremely large and pilose 

 or ciliated forceps. Such are, 1. The Porcellane larges pinces ; Can- 

 cer plalycheles, Pcnn., Brit. Zool., IV, vi, 12; Herbst., XLVII, 2, 

 where only the external margin of the forceps is pilose and the nearly 

 naked thorax is rounded; it is found on the rocks in the seas of 

 Europe. 2. The P. hirta, Lam., the whole superior surface of 

 whose forceps and thorax is pilose, and where the latter is nearly 

 oval and becomes thinner anteriorly. It was brought from King's 

 Island by Messrs, Peron and Lesueur. 



The forceps of the others are glabrous. Such is the Cancer hex- 

 apus, L. ; Herbst. XLVII, 4. The thorax is marked with short, 

 transverse, and slightly ciliated lines : the front trifid, with its middle 

 tooth finally notched. The claws are covered with little blood-red 

 scales and granules, the fingers separated and without internal den- 

 tations. It inhabits European seas f . 



The genus MONOLEPIS , Say, Journ. of the Acad. of Nat. Sc. of 

 Philad., I, 155; Desmar., Consid., p. 199 and 200, appears to con- 

 stitute the passage from the Porcellanye to the Megalopes. It ap- 

 proaches the first in the two posterior feet, and in the direction of the 

 tail. But this tail lias but six segments, and the eyes are very large 



* JEglee lisse, Desmar., Consider., xxxiii, 2 ; Latr., Encyclop. Method., Atl., 

 d'Hist. Nat. cccviii, 2. 



f See the article PorceUune, Nouv. Diet. d'Hist. Nut., Ed. 7 II. ; and Desmar., 

 Consid. sur les Crust., p. 192 199. 



