440 REPTILES a number of genera but failed in the attempt to arrange them in a natural or logical system. All the more remark- able, therefore, is the production by H. SCHLEGEL of an Essai sur la Physionomie des Serpens (Leyden, 1837; 2 vols. 8vo, with atlas in fol.). In this classical work the whole of the subject is treated throughout in a scientific manner ; the species are described with a clear discernment of really dis- tinctive characters, the description being generally accom- panied with a faithful outline figure of the head, and with a critical examination of the literature. Schlegel, besides, has the merit of having recognized the great importance of exactness with regard to localities, and of giving a general account of the geographical distribution of Snakes. The principle of classification adopted by Schlegel, indeed, is not one which will be recognized as final or even as legitimate at the present time, but it is one which is pre- ferable to that employed by Miiller, Dumeril, and Bibron, which led, as we shall see presently, to the most artificial grouping of species. He divided the Snakes into families according to their " physiognomy," that is " 1'impression totale que fait sur nous 1'ensemble d'un etre quelconque, impression que Ton peut sentir, mais qu'il est impossible de rendre au moyen de paroles ; elle est le re"sultat de I'harmonie de toutes les parties isolees, dont on embrasse la confirmation d'un coup d'oeil, et dans leurs rapports mutuels." Schlegel had no training in, or knowledge of, anatomy; he, therefore, ignored Miiller's researches which appeared a few years before his work; yet it is note- worthy that his classification stands in the main, and has not yet been superseded. He divides Snakes as follows : I. Non-venomous Snakes. Fam. 1. Burrowing. Gen. Tortrix. Fam. 2. Worm -like. Gen. Calamaria. Fam. 3. Terrestrial. Gen. Coronella, Xenodon, Hcterodon, Lycodon, Coluber, Herpetodryas, Psammophis. Fam. 4. Arboreal. Gen. Dcndrophis, Dryophis, Dipsas. Fam. 5. Freshwater. Gen. Tropidonotus, Homalopsis. Fam. 6. Boas. Gen. Boa, Python, Acrochordus. II. Venomous Snakes. Fam. 7. Colubriform. Gen. Elaps, Bungarus, Naja. Fam. 8. Marine Gen. Hydrophis. Fam. 9. Venomous Snakes proper. Gen. Trigonocephalus, Crotalus, Vipera. Already in 1832 J. MIJLLER had proposed "a natural classification of Snakes on anatomical principles," 1 in which he paid particular attention to the osteology of the hitherto dubious forms of Ophidians, but in the end based his arrangement entirely on the structure of the jaws and on the dentition. As he did not extend his examination into other parts of the organization of the various genera, it may suffice here to state that he divided all Snakes into two sections, the first of which (Ophidia microstomata) comprised the four families Amphisbxnoidea, Typhlopina, Uropeltacea, and Tortricina, and the second (Ophidia macrostomata) all the other Snakes, which he referred to seven families. The direction thus indicated by Miiller was followed by DUMERIL and BIBROX, who, however, by their much more detailed knowledge of Snakes, were enabled to subdivide the unwieldy categories formed by Miiller; also the genera which in Schlegel's system comprised Snakes with very different dentition had to be subdivided, and were defined with greater precision than had been done by any 1 Tiedemann's Zeitschr. /. Physiologic, vol. iv. p. 263 sq. [LITERATUI They divide Snakes into fi in one of .the jaws only : 2 famil Teeth in both jaws, none grooved: 12 famil Posterior maxillary teeth grooved : 6 fa previous herpetologist. equivalent sections 2 : 1. OPOTERODONTES. Teeth and 8 genera. 2. AGLTPHODONTES. and 86 genera. 3. OPISTHOGLYPHES. and 37 genera. 4. PROTEROGLYPHES. Anterior maxillary tooth grooved and fo lowed by other smooth teeth : 2 families and 16 genera. 5. SOLENOGLYPHES. Anterior maxillary teeth perforated and lated : 2 families and 13 genera. The progress made in ophiology from the time of the appearance of this work down to the present period consists rather in the increase of our knowledge of the great variety of species and genera than in the further development of the system. Gray, Reinhardt, Peters, Giinther, Cope, Bocage, Jan, Krefft, and others described a large number of forms, so that the number of those known to Dumeril and Bibron has now been perhaps trebled or quadrupled. Unfortunately, no general work corresponding to the present state of science exists. But two works published subsequently to the jfirpetologie generate are indispensable to the student. The first is the Catalogue of the Specimens of Snakes in the Collection of the British Museum, of which the first part, containing the Viperine Snakes, Water-Snakes, and Boas, by J. E. GRAY, appeared in 1849, and the second, containing the Colubrines, by A. GUNTHER in 1858. The classification, which was much behind its time, was fixed by the former of the two authors, so that the latter had to accommodate the arrangement of his part to that of his predecessor. However, he strongly opposed the application of the character of grooved posterior teeth to the formation of large sections, and generally adopted the principle advocated by Schlegel, whose generic groups were raised into families. A great number of Snakes unknown to Dumeril are described in these catalogues, whilst others which happened not to be represented in the British Museum are omitted. G. JAN in his Elenco sistematico degli Ofidi descritti e disegnatiper V Iconografia generale (Milan, 1863, 8vo) gene- rally adopts the families created by Giinther, but institutes under each two divisions, Aglyphodonta and Glyphodonta. Jan's great merit is the publication of his Iconographie generale des Ophidiens (Milan, 1 8 60-7 6 3 ), in which he figures all species which were in the Milan Museum or lent to him by other institutions, and which thus forms an invaluable aid in the determination of species. The author died during the progress of the work, but it was continued by his artist, Sordelli. No descriptive letter- press worthy of the name accompanies this work. The anatomy of Ophidians has hitherto received less attention than that of the other Reptilian orders. Be- sides the information contained in general works, we refer here only to two important special treatises : Rathke, Entwicklungsgeschichte der Natter, Kbnigsberg, 1839, 4to ; and Parker, On the Structure and Development of the Skull in the Common Snake (Tropidonotus natrix), London, 1879, 4to. Chelonians. Of ante-Cuvierian authors who paid n f* special attention to this suborder the following deserve lomau special mention : J. G. WALBAUM, 4 J. G. SCHNEIDER, 5 J. D. ScHOEPF, 6 and A. F. SCHWEIGGERJ Five or six 2 Dumeril changed the nomenclature adopted in his sixth volume when, eight years afterwards, he published the seventh after the death of Bibron. We give here the revised nomenclature. 8 The latest parts were issued without date between 1876 and 1882. 4 Chelonographia, oder Beschreibung einiger Schildkroten, Liibeck, 1782, 4to. 8 A llgemeine Naturgeschichte der Schildkroten, Leipsic, 1783, 8vo. 6 Historia Testudinum iconibus illustrata, Erlangen, 1792-1801, 4to (left incomplete by the death of the author). 7 Prodromi Monographise Cheloniorum sect, la et 2a, Konigsberg, 1814, 8vo.
