Part 643

The Pteropoda are divided into two orders: Cymnosomata, which have the body entirely naked and the head distinct from the wings; and Thecosomata, which have a delicate transparent shell of various forms, and the head not distinct from the wings.

Pte*rop"o*dous (?), a. (Zoˆl.) Of or pertaining to the Pteropoda.

Pter"o*saur (?), n. [Gr. &?; wind + &?; a lizard.] (Paleon.) A pterodactyl.

||Pter`o*sau"ri*a (?), n. pl. [NL.] (Paleon.) An extinct order of ||flying reptiles of the Mesozoic age; the pterodactyls; -- called also ||Pterodactyli, and Ornithosauria.

The wings were formed, like those of bats, by a leathery expansion of the skin, principally supported by the greatly enlarged outer or " little" fingers of the hands. The American Cretaceous pterodactyls had no teeth. See Pteranodontia, and Pterodactyl.

Pter`o*sau"ri*an (?), a. (Paleon.) Of or pertaining to the Pterosauria.

||Pter`o*stig"ma (?), n.; pl. Pterostigmata (#). [NL., fr. Gr. &?; wing ||+ &?;, &?;, a mark.] (Zoˆl.) A thickened opaque spot on the wings of ||certain insects.

Pte*ro"tic (?), a. [Gr. &?; wing + &?;, &?;, ear.] (Anat.) Of or pertaining to, or designating, a bone between the proˆtic and epiotic in the dorsal and outer part of the periotic capsule of many fishes. -- n. The pterotic bone.

The pterotic bone is so called because fancied in some cases to resemble in form a bird's wing

||Pte*ryg"i*um (?), n.; pl. E. Pterygiums (#), L. Pterygia (#). [NL., ||fr. Gr. &?;, properly a dim, akin to &?; a feather.] (Med.) A ||superficial growth of vascular tissue radiating in a fanlike manner ||from the cornea over the surface of the eye.

Pter"y*goid (?), a. [Gr. &?;, &?;, a wing + -oid.] (Anat.) (a) Like a bird's wing in form; as, a pterygoid bone. (b) Of, pertaining to, or in the region of, the pterygoid bones, pterygoid processes, or the whole sphenoid bone. -- n. A pterygoid bone.

Pterygoid bone (Anat.), a bone which corresponds to the inner plate of the pterygoid process of the human skull, but which, in all vertebrates below mammals, is not connected with the posterior nares, but serves to connect the palatine bones with the point of suspension of the lower jaw. -- Pterygoid process (Anat.), a process projecting downward from either side of the sphenoid bone, in man divided into two plates, an inner and an outer. The posterior nares pass through the space, called the pterygoid fossa, between the processes.

Pter`y*go*max"il*la*ry (?), a. [Pterygoid + maxillary.] (Anat.) Of or pertaining to the inner pterygoid plate, or pterygoid bone, and the lower jaw.

Pter`y*go*pal"a*tine (?), a. [Pterygoid + palatine.] (Anat.) Of or pertaining to the pterygoid processes and the palatine bones.

||Pter`y*go*po"di*um (?), n.; pl. Pterygopodia (#). [NL., fr. Gr. &?;, ||&?;, a fin + &?;, dim. of &?;, &?;, a foot.] (Anat.) A specially ||modified part of the ventral fin in male elasmobranchs, which serves ||as a copulatory organ, or clasper.

Pter`y*go*quad"rate (?), a. [Pterygoid + quadrate.] (Anat.) Of, pertaining to, or representing the pterygoid and quadrate bones or cartilages.

||Pte*ry"la (?), n.; pl. PterylÊ (#). [NL., fr. Gr. &?; feather + &?; ||wood, forest.] (Zoˆl.) One of the definite areas of the skin of a ||bird on which feathers grow; -- contrasted with apteria.

Pter`y*log"ra*phy (?), n. [Pteryla + -graphy.] (Zoˆl.) The study or description of the arrangement of feathers, or of the pterylÊ, of birds.

||Pter`y*lo"sis (?), n. [NL., fr. NL. & E. pteryla.] (Zoˆl.) The ||arrangement of feathers in definite areas.

Ptil"o*cerque (?), n. [Gr. &?; a feather + &?; tail.] (Zool.) The pentail.

||Ptil`o*pÊ"des (?), n. pl. [NL., fr. Gr. &?; a feather + &?;, &?;, ||offspring.] (Zoˆl.) Same as DasypÊdes.

Ptil`o*pÊd"ic (?), a. (Zoˆl.) Having nearly the whole surface of the skin covered with down; dasypÊdic; -- said of the young of certain birds.

||Pti*lop"te*ri (?), n. pl. [NL., fr. Gr. &?; a downy feather + &?; ||wing.] (Zoˆl.) An order of birds including only the penguins.

||Pti*lo"sis (?), n. [NL., fr. Gr &?; a feather.] (Zoˆl.) Same as ||Pterylosis.

Ptis"an (?), n. [L. ptisana peeled barley, barley water, Gr. &?;, from &?; to peel, husk; cf. F. ptisane, tisane.] 1. A decoction of barley with other ingredients; a farinaceous drink.

2. (Med.) An aqueous medicine, containing little, if any, medicinal agent; a tea or tisane.

Ptol`e*ma"ic (?), a. Of or pertaining to Ptolemy, the geographer and astronomer.

Ptolemaic system (Astron.), the system maintained by Ptolemy, who supposed the earth to be fixed in the center of the universe, with the sun and stars revolving around it. This theory was received for ages, until superseded by the Copernican system.