66 ZOOLOGY. 
seventy-six seconds. When the divers emerge, the face is strongly injected, 
and they often bleed freely from the nose, and sometimes from the ears and 
eyes. They dive three or four times in an hour, and upon emerging, they 
put on thick woollen cloaks. The sea is sufficiently clear to enable divers 
to see objects at the depth to which they go. 
The Phocidee (seals) remain fifteen minutes under water, having not only 
large lungs, but an adapting peculiarity in the Bee alatice: In a state of 
inaction ue can remain much longer, and when on land as much as two 
minutes sometimes elapses between each inspiration. According to 
Frederic Cuvier, the seals in the Paris collection sometimes slept with the 
head under water for an hour at a time, a period which exceeds that of a 
harpooned whale. In the case of the whale, however, there is great - 
muscular action, which requires more oxygen than a state of repose 
demands. 
S$ Dimyaria. 
The second section, Dimyaria, of the tribe Elatobranchia, includes the 
two sub-sections, *M/ytilacea and ** Cardiacea, the first of which includes 
the four families, 1. Mytilide ; 2. Arcidee ; 3. Unionidee; 4. Carditide. 
Fam. 1. Mytilide. This family includes the genera Mytilus (pl. 76, 
jig. 22) and several allied genera, and Pinna (figs. 18, 19). These 
animals have a linguiform foot, which secretes a byssus by which they are 
attached to rocks, the byssus being at first applied by the foot. The shell 
is equivalve, but very inequilateral, so that the umbones or beaks, which are 
usually situated about the middle of the back, are here placed at or near 
the anterior extremity of the shell. In Mytilus the lobes of the mantle are 
disunited, except at a single point posteriorly, which separates the anal 
siphon. ‘The anterior adductor muscle is much smaller than the posterior 
one. Lithodomus is a sub-cylindrical bivalve, which, in its young state, is 
suspended to rocks by a byssus ; but it subsequently perforates the rocks, 
and lives in a cavity but little larger than the shell, and then the byssus 
disappears. 
The genus Mytilus is used for food, under the name of mussel. Mytilus 
choros, which is found at Chiloe and other parts of the western coast of 
South America, attains a length of seven or eight inches; and as the animal 
is as large as the egg of a goose, and of a fine flavor, it is much esteemed. 
The favorite mode of cooking it is to make a fire upon flat stones in a pit, 
and when these are sufficiently heated, the fire and ashes are removed and 
the shell-fish deposited, and covered, first with leaves, &c., and then with 
clay. This mode of cooking is practised on the coast of Australia, and in 
the islands of the Pacific. | 
The common mussel, Mytilus edulis, is easily taken, as it lives in shallow 
water, and even between high and low water, upon both sides of the north 
Atlantic. The shell is smooth, and of a blue or violet color. This species 
is poisonous to some constitutions, perhaps one in a hundred, and it is 
possible that this quality depends somewhat upon the season. An emetic, 
followed by castor oil, is recommended when bad symptoms arise from 
eating this shell-fish. The symptoms appear in one or two hours, and they 
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