‘ 
Barnes on Batracian Animats and doubtful Reptils. 297 
ten, and which has been so much doubted. They are near- 
ly allied to the Lake Proteus, and yet perfectly distinct. 
Dr. Harlan seems to think that they “have every character- 
istic of Salamanders.’ I, on the contrary, think them unlike 
species here enumerated. . 
The singular and compound structure of the respiratory 
organs has been a fruitful source of doubt and disputation. 
The truth at last seems to be, that the air is inspired by the 
nostrils into the air sacks, and reserved for use while the ani- 
al is in the mud, or under the water, and slowly expired by 
the gills or spiracles. The lining membrane of the mouth 
closes the posterior nares, and prevents the escape of the air, 
and the persistent operculum closes the opening of the gills, 
and prevents the influx of the water. The fringed gills may 
be useful in keeping a free space around the opening, so that 
the animal may not be strangled by lateral pressure. The 
may also, in the water, perform an office similar to that of 
mastaces or tentacula in other animals. Thus organized, the 
animal is remarkably fitted to his habitation and circumstan- 
“eS 
has fallen into the common-error of supposing that the ho 
lotl is an immature Salamander. a 3 
VOLe RENO. EE 38 
