VOL. LVI.] PHILOSOPHICAL TRANSACTIONS,' 329 



dered capable of living a considerable time on shore, otherwise their loco-motion 

 would be vain. How is this provided for? why in a most convenient manner; 

 for this order of fishes have their branchiae well covered from the external drying 

 air, and are also furnished with a slimy mucus, which hinders their becoming 

 crisp and dry for many hours, and their very skins always emit a mucus liquor, 

 which keeps them supple and moist for a long time; whereas the branchiae of 

 other kinds of fish are much exposed to the air, and want the slimy matter to 

 keep them moist. Now if, when any of these is brought out of the water, it 

 was laid in a vessel without water, he might be kept alive a considerable time, by 

 only keeping the gills and surface of the skin constantly wet, even without any 

 water to swim in. 



Dr. P. mentions something that relates to a family among the fish kinds, which 

 is of a middle nature between the phocae, and the real fishes of the sea, in one 

 peculiar respect. This is the class of the phocenae, or porpoises, of which there 

 are several species; and these have lungs, and therefore are forced to come up to 

 the surface to breathe at very short intervals; but, when brought on shore, have 

 no progressive loco-motion. So that, having lungs, they resemble the phocae, 

 and in every other respect, the real fishes of the sea. Blasius, in his Anatome 

 Animalium, p. 288, gives an account of one of these taken and brought on 

 shore alive; the people let him lie, to see how long he could live out of the 

 water; and he continued alive only about 7 or 8 hours, and exhibited a kind of 

 hissing voice. 



From what has been said. Dr. P. hopes it will appear rational, that these are 

 the only two orders that can properly be deduced from the class of amphibious 

 animals; and that the genuses of either order are very few in the animal world. 



XXI f^. An Account of some peculiar Advantages in the Structure of the As- 

 perte Arteries, or Wind Pipes, of several Birds, and in the Land Tortoise. 

 By Dr. Parsons, F. R. S. p. 204, 



Dr. P. having in the former discourse given an account of some particular 

 phenomena in amphibious animals, which rendered them more happy and per- 

 fect in their animal economy towards their preservation ; he now lays before the 

 B. s. certain advantages in some birds, towards assisting them in the acquisition 

 of their food, which they seek for in the water; and some of these swim on the 

 water and dive down occasionally; others only wade into the water, in shallow 

 places, as far as their long legs will carry them, without touching the water with 

 their feathers, in search of their nourishment. 



The natural history of 4 of them is very well set forth by authors; the other 

 2 are not mentioned, but barely by their names; and though the author has not 

 described them, yet he knew the structures of their asp^rae arteriae, and was a 



VOL. XII. U u 



