280 SUPPLEMEXT 



Sciences, has collected the following observations respecting 

 this animal. 



" It was on the 28th day of July, 1812, that T had occasion 

 to see and observe this curious crustaceum, on visiting the 

 celebrated degorgeoir of the Lake of Albano, otherwise the 

 Lake of Castello. It is known that the basin of this lake is 

 considered by most travellers, and even naturalists, to be 

 the crater of an ancient volcano. It is five miles in circuit, 

 and as much as four hundred and eighty feet of depth is 

 given to the water which fills the lower part. This water 

 is limpid, perfectly sweet, and is inhabited by divers kinds 

 of fresh-water fish, common frogs, &c. The redundancy 

 of water runs off incessantly in a gi'eat stream by this ad- 

 mirable subterraneous canal, which is almost two miles 

 long, and which has been preserved, without deterioration, 

 from the earliest times of Rome. The heat which reigned in 

 the atmosphere when I was in this part of the country, the 

 purity of the water, the solitude, the shade, and fi-eshuess of 

 the shore, the bottom of which could be discovered there, to 

 a very great distance from the edge, like a strand, induced me 

 to bathe, and it was thus that I chanced to catch three or four 

 individuals of the species of crab in question. 



"I was very much surprised at the first appearance of these 

 crabs, not being by any means jDrepared for it. They ap- 

 peared to me so similar in figure, size, gait, &c. to those 

 which are commonly found on maritime shores, in fine, to the 

 Cancer moenas, that I imagined at first that they might be 

 those identical crabs, which had been brought from the sea, 

 which is not, in fact, very distant, as an attempt to naturalize 

 them in this lake, and that this attempt had succeeded. 

 Nevertheless, I remarked that they had a whitish or livid 

 colour, whereas the marine ones to which I was comparing 

 them are brown. Afterwards, perceiving scattered here and 

 there some carapaces, and other old remains of these crabs, 



