See Embryology.


See Piacenza.


Placoids (Gr. Placoids 1300550 , to cover with plates), a division of cartilaginous fishes in the old system of Agassiz, including the sharks and rays, characterized by a skin covered irregularly with enamelled plates, or studded with rough osseous points sometimes furnished with little hooks, and resembling the peculiar surface of shagreen. They are among the highest of fishes, approaching reptiles, and many of them are viviparous. (See Comparative Anatomy, and Plagiostomes).


See Flounder.


Plainfield, a city of Union co., New Jersey, on the Central New Jersey railroad, 24 m. W. S. W. of New York; pop. in 1860, 3,224; in 1870, 5,095. It is beautifully laid out. Many of the residents are engaged in business in New York, and very little manufacturing is carried on. A large amount is annually expended for the support of the public school, which ranks among the first in the state. There are two national banks, a savings institution, two weekly newspapers, and nine churches.

Planer Tree

See Elm.

Plant Louse

See Aphis.


Plantigrades, a division of carnivorous mammals, so named because the whole foot, including the tarsus and metatarsus, is applied to the ground in walking. The toes are longer than in the digitigrade division, the form heavier, and the diet more vegetable; they have a greater facility for raising themselves on their hind feet, for clasping, climbing, and digging; the small extent of the lumbar region renders them less supple and agile; they are generally slow in their movements, and nocturnal in habit. The distinctions between these divisions are not entirely definite, and some animals are intermediate between the two, and therefore semi-plantigrade; these divisions may be represented respectively by the bears, the dogs and cats, and the civets and weasels. Besides the bears, the plantigrades embrace the glutton or wolverene, badger, raccoon, coaiti, kinkajou or potto, and the panda or wah.


Plaquemines, a S. E. parish of Louisiana, at the extremity of the state, bordering on the gulf of Mexico, and including the delta of the Mississippi, by which it is intersected; area, about 1,000 sq. m.; pop. in 1870, 10,552, of whom 6,845 were colored. It has a low and level surface, nowhere more than 10 ft. above the gulf, and a large portion is occupied by marshes. The chief productions in 1870 were 55,280 bushels of Indian corn, 7,723 hogsheads of sugar, 421,562 gallons of molasses, and 8,639,026 lbs. of rice. There were 914 horses, 1,648 mules and asses, 1,116 milch cows, 2,236 other cattle, and 1,111 swine. Capital, Point a la Hache.

Plaster Of Paris

See Gypsum.

Plaster Of Paris #1

See Gypsum.

Platon Levshin

Platon Levshin, a Russian prelate and historian, born near Moscow in July, 1737, died there, Nov. 23, 1812. He was rector of a seminary, and wrote a manual of the dogma of the eastern orthodox church (St. Petersburg, 1765), which has been translated into foreign languages. In 1775 he was made archbishop of Moscow, and in 1787 received the title of metropolitan. He was an eloquent preacher. His works include a history of the Russian church (2 vols., Moscow, 1805; 2d ed., 1823), and 20 volumes of sermons. His biography was written by Snegireff (Moscow, 1831; new ed., 2 vols., 1856).