Page:Encyclopædia Britannica, Ninth Edition, v. 20.djvu/99

Rh P T O P T O 87 limb is small, and the fibula seems to have been feebly developed and fixed to the tibia. The hind foot has five digits in. some forms, but only four in others. In the latter case the number of phalanges to each digit, counting from the tibial side, is two, three, four, five respectively. The long bones and vertebrae, as well as some parts of the skull, contained large pneumatic cavities similar to those found in birds. There can be little doubt that the ptero- dactyles had the power of sustained flight. The large size of the sternal crest indicates a similar development of the pectoral muscles and a corresponding strength in the arms. The form of the forelimb, especially its outer digit, indi- cates in no uncertain 'manner that it supported a flying membrane ; but within the last few years this has been more clearly demonstrated by the discovery of a specimen in the Solenhofen slates with the membrane preserved (fig. 2). The occurrence of pterodactyle remains in marine deposits would seem to indicate that they frequented the seashore ; and it is tolerably certain that those forms with long and slender teeth were, in part at least, fish-eaters. Seeing, however, that the armature of the jaws varies considerably in the different genera, it is most likely that their diet varied accordingly. Pterodactyles present so many avian peculiarities that it has been proposed to place them in a special group, to be called Ornithosauria, which would hold a position intermediate between Aves and Reptilia. On the other hand, pterodactyles are thought by most authorities to have a closer relationship with the reptiles, and the different genera are placed in a separate order of the Reptilia called Ptero- sauria. The most important genera are five. (1) Pterodactylus; these have the jaws pointed and toothed to their extremities, and the tail very short. (2) Rhamphorhynchus (fig. 2) ; this genus has the jaws provided with slender teeth, but the extremities of both mandible and upper jaw are produced into toothless beaks, which were prob- ably covered with horn ; the tail is extremely long. (3) Dimor- pkodon ; in this form the anterior teeth in both upper and lower jaws are long, but those at the hinder part of the jaws are short ; the tail is extremely long. (4) Pteranodon ; similar in most respects to Pterodactylus, but the jaws are devoid of teeth. In these four genera the outer digit of the manus has four phalanges. (5) Orni- thoptcrus ; this form is said to have only two phalanges in the outer digit of the manus ; the genus, however, is very imperfectly known, and it has been suggested that it may perhaps be a true, bird. The Pterosauria are only known to have lived during the Meso- zoic period. They are first met with in the Lower Lias, the Dimor- phodon macronyx from Lyme Regis being perhaps the earliest known species. The Jurassic slates of Solenhofen have yielded a large number of beautifully preserved examples of Pterodactylus and PJiampJiorhynchus, and remains of the same genera have been found in England in the Stonesfield slate. Bones of pterodactyles have also been obtained in some abundance from the Cretaceous phosphatic deposits near Cambridge ; and their remains have been met with occasionally in the Wealdeu and Chalk of Kent. The genus Pteranodon is only known from the Upper Cretaceous rocks of North America. The Pterosauria were for the most part of moderate or small size (see fig. 1), but some attained to very con- siderable dimensions ; for instance, Rhamphorhynchus Bucklandi from the Stonesfield slate probably measured 7 feet between the wing-tips. But the largest forms existed apparently towards the close of the Mesozoic period, the pterodactyles of the British Cretaceous rocks and the American Pteranodon being of still larger size : some of them, it is calculated, must have had wings at least 20 feet in extent. See Buckland, Bridge-water Treatise, 1836 ; Cuvier, Ossements fossiles, vol. v. pt. 2, p. 359(1824); Huxley, " On Rhamphorhynchus Bucklandi," in Quart. Journ. Geol. Soc., vol. xv. p. 658 (1859), and Anatomy of Vertebrated Animals (1871), p. 266 ; Marsh, " Notice of New Sub-order of Pterosauria (Pteranodon)," Amer. Journ. Sci. and Art, vol. xi. p. 507 (1876), and on the "Wings of Pterodac- tyles," in Amer. Journ. Science, vol. xxiii. p. 251 (1882) ; Owen, Palxonto- graphical Society (1851, 1859, 1860) ; Seeley, Ornithosauria (1870) ; Von Meyer, Reptilien aits dem lithograph. Schiefer [Fauna der Voruxlt] (1859), and Palssonto- grapUca, vol. x. p. 1 (1861). (E. T. N.) PTOLEMIES, the Macedonian dynasty of sovereigns of Egypt. See EGYPT, vol. vii. pp. 745-748, and MACE- DONIAN EMPIRE, vol. xv. p. 144. PTOLEMY (CLAUDIUS PTOLEM^US), celebrated as a mathematician, astronomer, and geographer. He was a native of Egypt, but there is an uncertainty as to the place of his birth ; some ancient manuscripts of his works describe him as of Pelusium, but Theodorus Meliteniota, a Greek writer on astronomy of the 12th century, says that he was born at Ptolemais Hermii, a Grecian city of the Thebaid. It is certain that he observed at Alexandria during the reigns of Hadrian and Antoninus Pius, and that he sur- vived Antoninus. Olympiodorus, a philosopher of the Neoplatonic school who lived in the reign of the emperor Justinian, relates in his scholia on the Phxdo of Plato that Ptolemy devoted his life to astronomy and lived for forty years in the so-called Hrepa. rov KavwfBov, probably elevated terraces of the temple of Serapis at Canopus near Alexandria, where they raised pillars with the results of his astronomical discoveries engraved upon them. This statement is probably correct ; we have indeed the direct evidence of Ptolemy himself that he made astronomical ob- servations during a long series of years ; his first recorded observation was made in the eleventh year of Hadrian, 127 A.D., 1 and his last in the fourteenth year of Antoninus, 151 A.D. Ptolemy, moreover, says, "We make our obser- vations in the parallel of Alexandria." St Isidore of Seville asserts that he was of the royal race of the Ptolemies, and even calls him king of Alexandria ; this assertion has been followed by others, but there is no ground for their opinion. Indeed Fabricius shows by numerous instances that the name Ptolemy was common in Egypt. Weidler, from whom this is taken, also tells us that according to Arabian tradition Ptolemy lived to the age of seventy-eight years ; from the same source some description of his personal appearance has been handed down, which is generally considered as not trustworthy, but which may be seen in Weidler, Historia Astronomic, p. 177, or in the preface to Halma's edition of the Almagest, p. Ixi. Ptolemy's work as a geographer is treated of below (p. 91 sq. and an account of the discoveries in astronomy of Hipparchus and Ptolemy has been given in the article ASTRONOMY. Their contribu- tions to pure mathematics have not yet been noticed in the present work. Of these the chief is the foundation of trigonometry, plane and spherical, including the formation of a table of chords, which served the same purpose as our table of sines. This branch of mathematics was created by Hipparchus for the use of astronomers, and its exposi- tion was given by Ptolemy in a form so perfect that for 1400 years it was not surpassed. In this respect it may be compared with the doctrine as to the motion of the heavenly bodies so well known as the Ptolemaic system, which was paramount for about the same period of time. There is, however, this difference, that, whereas the Ptole- maic system was then overthrown, the theorems of Hip- parchus and Ptolemy, on the other hand, will be, as Delambre says, for ever the basis of trigonometry. The astronomical and trigonometrical systems are contained in the great work of Ptolemy 'H /j.adrjfj.ariKr) O-WTU^I?, or, as Fabricius after Syncellus writes it, MeyaA^ o-uvra^ts TTJS dcrr/oovo/Aias; and in like manner Suidas says OVTOS [II-ToA.] eypa^e rov p.eyav dcrrpovofwv -tjroi crvvraiv. The Syntaxis of Ptolemy was called C O /ttyas acrr/Dovd/xos to distinguish it from another collection called '0 /ii/c/aos do-r/>ovo/zo?, also highly esteemed by the Alexandrian school, which con- tained some works of Autolycus, Euclid, Aristarchus, Theo- dosius of Tripolis, Hypsicles, and Menelaus. To designate the great work of Ptolemy the Arabs used the superlative fj.eyia-Tf), from which, the article cd being prefixed, the hybrid name Almagest, by which it is now universally known, is derived. We proceed now to consider the trigonometrical work of Hippar- chus and Ptolemy. In the ninth chapter of the first book of the Almagest Ptolemy shows how to form a table of chords. He sup- poses the circumference divided into 360 equal parts (r/j.rifj.ara), and then bisects each of these parts. Further, he divides the diameter 1 Weidler and Halma give the ninth year ; in the account of the eclipse of the moon in that year Ptolemy, however, does not say, as in other similar cases, he had observed, but it had been observed (Almagest, iv. 9).