43 O DESCRIPTION OF THE MUSEUM. 



whence it was sent to us by M. Lesueur, the 

 foliated polyodon, so called because the edges of 

 its snout are furnished with a small membrane 

 reticulated by a great number of vessels which | 

 resemble the fibres of leaves. 



The fishes which we have hitherto seen are 

 cartilaginous ; those which follow belong to 

 another series, the osseous. The first family is 

 that of the gymnodontes, which consists of three 

 genera : diodon, tetrodon, and mole. The first com- 

 monly called spiny orbs, or sea porcupines, have 

 the body covered with long quills ; they have 

 the power of inflating themselves into the form 

 of a ball, and float upon the water ; the second 

 have their body covered with shorter prickles. 

 We have fifty-four species of them. One of 

 the most remarkable is the fahaca of the Arabs 

 [tetrodon physsa, Geoff. St.-Hilaire) : during the 

 inundations of the Nile a great number are cast 

 upon its banks. The third genus comprehends 

 the species vulgarly called moon-fish : their body- 

 is compressed and without prickles, and their 

 tail is very short. Amongst the four species in 

 the Museum, that of our seas, which is of a sil- 

 very colour, weighs sometimes three hundred 

 pounds ; there are two specimens of it attached 

 to the ceiling. 



The next family, that of the sclerodermas,, com- 



