478 



PTERODACTYL 



PTOLEMY 



with in the Jurassic and Cretaceous systems. 

 There are numerous forms of Pterodactyl which 

 are include<l in the extinct order Ornitiiosniiria. 

 The head was relatively large and snout-like, tin' 

 Ion); jaws Ix-ing furnished with simple and pointed 

 teeth, implanted in separate sockets. Tne eye- 

 orbit was very large, the sclerotic having generally 

 a ring of bony plates, and the nostrils approxi- 

 mated to the orhits. The neck was long and bird- 

 like, consist in;,' of proco-lous vcrlehne which were 

 longer than the dorsals the latter varying from 

 seventeen to twenty in number. From three to 

 six vertebrae are anchylosed to form the, sacrum. 

 The tail is generally short, hut long-tailed forms 

 are also met with. The scapular arch and keeled 



Pterodactylus crassirostris. 



sternum in their general characters resemble those 

 of the carinate birds. There are four digits on each 

 limb the outer digit of the nianns (corresponding 

 to the fifth of the typical series ) l>eing immensely 

 elongated for the support of a membranous expan- 

 sion (potagium ), which was also attached to the 

 sides of the body to embrace the hind limbs and 

 tail. The other digits of fore and hind limbs ter- 

 minated in curved claws. Most of the bones are 

 hollow like those of birds. The body was probably 

 naked. 



Many forms of Pterodactyl are known, in some 

 of which tli" skull is less bird -like than that 

 shown in the accompanying illustration. In 

 Ilhamphorbyncus the extremities of the jaws are 

 usually edentulous, and were perhaps sheathed in 

 horn ; the base of the jaws, however, was furnished 

 with teeth which were inclined forwards. In the 

 same form the tail was long, and provided at the 

 extremity with a leaf-like steering membrane. In 

 Pimorphodon the jaws are provided with strong 

 teeth in front and much shorter ones behind ; and 

 the. tail was long. 



Some pterodactyls were small Ptenodraco being 

 not larger than a sparrow. Others were about the 

 size of a woodcock. Yet others, however, were 

 much larger some having a spread of wing of 5 or 

 6 feet, and even of 25 feet in the case of certain 

 forms from the Cretaceous rocks of England. The 

 form of it extremities shows that ' the Pterodac- 

 tyl was capable of perching on trees, of hanging 

 against perpendicular surfaces, and of standing 

 firmly on the ground, when, with it* wings folded, 

 it might crawl on all fours, or hop about like a 

 bird.' 



Ornithosaurians are well represented in the 

 Mesozoic strata of Europe and North America. 

 One of the richest repositories of their remains is 

 the famous lithographic stone of Solenhofen, in 



which the fossils usually occur in a fine state of 

 i>ree/vation even the impression of the mem- 

 branous wing being sometimes clearly seen. See 

 Nicholson and Lydekker'a I'alcrontology. 



Pteromys. See FLYING ANIMALS. 



I'lero'poda (<ir., wing-footed'), a class or 

 sub-class of molluscs, having two lobes of the 

 'foot' developed into wing-like swimming organs. 

 They live in the open sea, and are carnivorous. 

 Distributed in all seas, they often occur in immense 

 shoals, and afford food to fishes and Cetaceans. 

 The body is bilaterally symmetrical, but this is 

 doubtless secondarily acquired. In some (Thecoso- 

 mata) the viscera are covered with a delicate shell ; 

 the others ((iynmosomata) are naked, but all 

 the larva; have shells. The thin calcareous or 

 gristle-like shells are abundant in the Ooze 

 (q.v.) of some regions. It is very likely that 

 the Pteropods should be ranked not as a 

 separate class of molluscs, but as a sub-class 

 of Gasteropods. Of the Thecosomata tin- 

 genera Hyalea and Cymbulia are representa- 

 tives, as Clio and I'ncumodcrmon are of 

 (lymnosomata. Fossil Pteropods appear even 

 in the Cambrian strata. See Pelseneer, 

 i '/ml/, HI/IT Report (1889). Some Pteropods 

 are sometimes called 'sea- butterflies." 

 Ptolemaic System. See PTOLEMY. 

 Ptolema'is. See ACRE (Sr JEAN i>'). 

 Ptolemy, name of the Macedonian kings 

 of Egypt. The first, a son of Lagos, was 

 called Soter ('Saviour') by the Rhodians, 

 whom he defended against Demetrius Polior- 

 cetes. He became one of the greatest of the 

 generals of Alexander the Great (q.v.), and 

 on Alexander's death became ruler of Egypt. 

 For the other Ptolemies, his successors, see 

 EGYPT, Vol. IV. p. 241 ; and for their patronage 

 of literature, ALEXANDRIAN SCHOOL. 



Ptolemy, properly CLAUDIUS PTOLEM^US, a 

 celebrated astronomer and geographer, was a 

 native of Egypt, though it is uncertain whether 

 he was born at Pelusiuin or Ptolemais in the 

 Thebaid. Nothing is known of his personal 

 history, except that he flourished in Alexandria 

 in 139 A.D., and there is prol>able evidence of 

 his having been alive in 161. The chief of his 

 writings are the MpydXij SiVrafis TTJ? 'AaTporo/iiat, 

 which, to distinguish it from the next mentioned, 

 seems to have been denominated by the Greeks 

 and by the Arabs after them megiste, ' the 

 greatest,' whence was derived the name Almagest 

 (with Arab article <d, 'the'), by which it is gener- 

 ally known ; the Tctrabiblos Si/nfn.ri.i, with which 

 is combined another work called Karpos or t'ni/i- 

 loquinm, from its containing a hundred aphorism* 

 1 >oth works treating of astrological sulijects, ami 

 held by some on this account in be of doubtful 

 genuineness ; a treatise on the phenomena of the 

 fixed stars, or a s|>ecies of almanac ; and the Geo- 

 graphia, his great geographical work, in eight 

 OOOKS. The rest of nis works are of inferior im- 

 portance, and consist of descriptions of various 

 kinds of Projections (q.v.). the theory of the musi- 

 cal scale, chronological and metaphysical treatises, 

 and a summary of the hypotheses employed in his 

 great work, the Almagest. 



Ptolemy, Ixrth as an astronomer and geographer, 

 held supreme sway over the minds of almost all the 

 scientific men from his own time down till tin' 



16th-17th century; but, and in astronomy specially, 

 he seems to have lieen not so much an independent 

 investigator as a corrector and improver of the 

 work of his predecessors. In astronomy In- de- 

 pended almost entirely on the labours of ]!i|ipar- 

 chus. But, as his works form the only remainin;: 



