PTARMIGAN 374 PTEROSAURIA what he is not. Psychoanalysis (q. v,), is an extended form of his re-education, and involves the moral rehabilitation of the patient by leading him through free association to bring his vi^hole mind into the open, hovi^ever reluctant he may be in doing so, and thus reveal the re- pressed desires, of which, according to the theory of Freud, the neurotic mani- festations are the outward symbols and expressions. PTABMIGAN, Lagopus mutus, a game bird found in the N. of Europe, especially in Norway and Sweden, and in the United States. In winter the plumage of the male is almost wholly white, with a small patch behind the eye; ROCK PTARMIGAN A. Summer Plumage B. Winter Plumage the shafts of the primaries and the bases of the exterior tail-feathers are black, and there is a patch of bare red skin around the eye. In the summer the black retains its position, but the white is mottled and barred with black and gray. The length of the adult male is rather more than 15 inches. Their call is a harsh croak. PTERASPIS, a genus of Placodermi, having the cephalic shield finely grooved and composed of seven pieces. It had a rostrum in front, and its lateral angles were produced so as to form short cor- nua. So far as is known, it is the most ancient fish form, two species being known from the Upper Silurian, and six from the Lower Devonian of Orkney and Perthshire, Scotland. PTERICHTHYS, a genus of Placo- derms, discovered by Hugh Miller in the Old Red Sandstone. The head and ante- rior part of the trunk were defended by a buckler of large ganoid scales, united by sutures, the cuirass articulating at the sides with a back plate; the rest of the body covered vdth small ganoid scales. Pectorals long and wing-like, a scaly short tail. Twelve species; eight from the lower, and four from the Up- per Devonian of Orkney, Cromarty, Caithness, Scotland, and in Ireland. PTERIS, in botany, a genus of Poly- podese. Sori continuous, linear, margi- nal; involucre scarious or membranous, confluent with the recurved margin of the frond. Known species 80, of world- wide distribution. PTEROCARPUS, in botany, a genus of Dalhergieae, having a thin wing at the edge of the fruit. Large trees, chiefly from the tropics. P. marsupium, P. indicus, and P. macrocarpus furnish East Indian kino, and P. eriiiaceus, Af- rican kino, P. draco and P. santalinus, red sandal wood. P. balberggioides, a good Indian wood, and P. indicus, the ex- cellent Andaman red wood. Cattle and goats feed on the leaves of P. m,arsupium. PTEROCERAS, in zoology, scorpion shell, or spider shell. Shell, when young, like that of Strombus; afterward the outer lip becomes prolonged into several long claws, one of them forming a pos- terior canal. Recent species 12, from India or China. PTERODACTYL, a remarkable genus of fossil lizards, peculiar to the Mesozoic strata. Collini, and other more eminent naturalists, referred it to the mammalia, finding its nearest ally in the bat. The careful investigations of Cuvier, how- ever, showed that the pterodactyl was a true lizard, but possessed of the power of flight. PTEROPODA, in zoology, a class of Cuvier's embranchement of sub-king- dom Mollusca. Also, a sub-class of Ce- phalopoda, in which the mid-region of the foot is drawn out into a pair of wing- like muscular lobes, used as paddles. The hind region is often absorbed, but may carry an operculum; the fore region is sometimes drawn out into tentacles, provided with suckers. There are two orders: Thecosomata and Gyninoso- mata. PTEROSAURIA, an order of flying Reptilia of Mesozoic age. No exoskele-
