DECAPODA. 31 



almost shaped like a truncated heart, and the tarsi are furnished 

 with spinous or dentated ridges. 



Several species are known, all of which inhabit fresh water, 

 but capable, as it would appear, of living at a distance from it 

 for a considerable time. One of them, mentioned by the an- 

 cients, is found in the south of Europe, the Levant, and in 

 Egypt; it is the Crabe fluviatile, of Belon, Rondelet, and Ges- 

 ner(l). It is very common in several brooks and various lakes 

 of the craters of the south of Italy; its effigy is observable on 

 different antique Grecian medals, particularly on those of Si- 

 cily. The shell is about two inches in each diameter. It is 

 greyish or yellowish, as the animal is living or dead, mostly 

 smooth, with little incised rugae and asperities on the anterior 

 sides. The front is transversal, inclined, reflected, and eden- 

 tated. The claws are rough, with a reddish spot at the extrem- 

 ity of the fingers, which are long, conical, and unequally den- 

 tated. The Greek monks eat it raw, and during lent it forms 

 one of the articles of diet used by the Italians. 

 Two naturalists, travellers of the government, prematurely taken 

 from the sciences, Delande and Leschenault-de-Latour, discover- 

 ed two other species; one was collected by the first in his travels to 

 the south of Africa, and the other by the second in the mountains of 

 Ceylon. 



The Cancer senex of Fabricius (Herbst., XL, 5), should, in my 

 opinion, be referred to the same subgenus. It inhabits the East 

 Indies. 



A species peculiar to America, the Thelphusa serrata, Herbst., 

 X, ii, is proportionably wider and flatter than the others, pre- 

 senting certain characters which seem to indicate a particular 

 division(2). 

 Other Quadrilatera having, like the preceding ones, the fourth 

 joint of the external foot-jaws inserted in the internal extremity of 

 the previous joint, differ from them in the trapezoidal, transverse and 



(1) See Olivier Voy., en Egypte, pi. xxx, 2; and the plates of Nat. Hist, in the 

 great work on that country. 



(2) See also the subgenus Octpode. I have made a new one called Tmciio- 

 dactylus, with a fresh-water species from Brazil analogous to the preceding ones, 

 but with an almost square shell, the third joint of the external foot-jaws forming 

 an elongated triangle hooked at the end, and the tarsi covered with a close down. 



The Graspus tesselatus, of the pi. (cccv, 2) of Nat. Hist., Encyc. Method., is 

 also the type of the new genus Melia, but one of too little importance to be 

 treated of in detail in a work like this. 



