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AMPHIBIA — AMPHIOXUS

additional segment in the hind limb. Caudal vertebrae fused into a urostyle or coccyx. Frontal bones confluent with parietals. This order embraces about 1300 species, oi which some 40 are fossil, divided into two sub-orders and sixteen families :— A. Aglossa.—Eustachian tubes united into a single ostium pharyngeum ; no tongue. Dactylethrid.®, Pipid,*. B. Phaneroglossa. — Eustachian tubes separated ; tongue present. Discoglossid^!, Pelobatid^:, Hemipiiractim:, AmphiGNATHODONTID^}, HyLID.®, BuFONID.®, Dendrophryniscidj®, Oystignathid®, Dyscophid®, Genyophrynib®, EngySTOMATID®, CERATOBATRACHIB®, RaNib®, Denbrobatib®. The Phaneroglossa are divided into two groups: Arcifera and Firmisternia, representing two stages of evolution. The family characters are mainly derived from the dilatation or non - dilatation of the sacral diapophyses, and the presence of teeth in one or both jaws, or their absence. The Discoglossidce are noteworthy for the presence of short ribs to some of the vertebrae, and in some other points, also, they approach the tailed batrachians ; they may be safely regarded as, on the whole, the most generalized of known Ecaudata. Distinct ribs are present at an early age in the Aglossa, as discovered by Ridewood (22). The recent addition of a third genus of Aglossa, Hymenochirus (23) from tropical Africa, combining characters of Piya, and ] Pio. 5.—Vertebral column Xenopus, has removed every doubt as to viewfmeTO°CMrMS ^ventral the real affinity which connects these genera. Hymenochirus is further remarkable for the presence of only six distinct pieces in the vertebral column, which is thus the most abbreviated among all vertebrata (Fig. 5). Apart from a few unsatisfactory remains from the Eocene of Wyoming, fossil tailless batrachians are only known from the Oligocene, Miocene, and Pliocene of Europe and India. These forms differ very little from those that live at the present day in the same part of the world, and some of the genera (Discoglossus, Bufo, Oxyglossus, liana) are even identical. Falceobatrachus (24), of which a number of species represented by skeletons of the perfect form and of the tadpole have been described from Miocene beds in Germany, Bohemia, and France, seems to be referable to the Pelobatidce; this genus has been considered as possibly one of the Aglossa, but the absence of ribs in the larvae speaks against such an association. Since the publication of the article Amphibia numerous additions have been made to our knowledge of the development and nursing habits, which are extremely varied, some forms dispensing with or hurrying through the metamorphoses and hopping out of the egg in the perfect condition (25). (1) On the use of the names Batrachia and Amphibia, cf. E. D. Cope, Geol. Mag. (3) ii. 1885, p. 575 ; G. Baur, Science [2) vi. 1897, pp. 170, 372 ; B. G. Wilber, t. c. p. 295; T. Gill, t. c. p. 446 ; 0. P. Hay, t. c. p. 773. (2) E. Fraas, “Die Labyrinthodonten der Schwabischen Trias,” Palceontogr. xxxvi. 1889, p. 1. (3) E. D. Cope, “ Synopsis of the Extinct Batrachia of North America.” Proc. Ac. Philad. 1868, p. 208. (4) “Researches on the Structure, Organization, and Classification of the Fossil Reptilia, vii.” Phil. Trans, clxxxiii. (B) 1892, p. 311. (5) “ Die Urvierfiissler {Eotetrapoda) des Sachsischen Rothliegenden.” Allgem. verstdndl. naturh. Abh., Berlin, 1891, No. 15. (6) H. Crebner. “ Die Entwickluugsgeschiehte von Branchiosaurus amblystomus.” Zeitschr. Deutsch. Geol. Ges. 1886, p. 576. (7) C. Emery. “Ueber die Beziehungen des Chiropterygium zum Ichthyopterygium.” Zool. Anz. x. 1887, p. 185.— E. D. Cope. “ On the Phylogeny of the Vertebrata.” Proc. Amer. Philos. Soc. xxx. 1892, p. 280.—H. B. Pollarb. “On the Anatomy and Phylogenetic Position of Polypterus.” Zool. Jahrb. Anal. v. 1892, p. 414.—G. Baur. “ The Stegocephali: a Phylogenetic Study,” Anal. Anz. xi. 1896, p. 657.—L. Dollo. “ Sur le Phylogenie des Dipneustes.” Mem. Soc. Beige Geol. ix. 1895, p. 79.—T. Gill. “On the Derivation of the Pectoral Member in Terrestrial Vertebrates.” Bep. Brit. Ass. 1897, p. 697. (8) E. D. Cope. “The Origin of the Mammalia.” Proc. Amer. Philos. Soc. xxii. 1884, p. 43.—Cf. Discussion on Origin of Mammals, Proc. Intern. Congr. Zool., Cambridge, 1898. (9) A. Fritsch. Fauna der Gaskohle und der Kalksteine der Perm formation Bohmens. Vols. i. and ii. Prague: 1879-85, 4to. —H. Crebner. “ Die Stegocephalen aus dem Rothliegenden des Plauensohen Grundes bei Dresden.” Zeitschr. Deutsch. Geol. Ges. 1881-1894.—J. W. Dawson. “On the Results of Recent Explorations

of Erect Trees containing Animal Remains in the Coal Formation of Nova Scotia.” Phil. Trans. (Axxiii. 1882, p. 621.—H. B. Geinitz and J. V. Deichmuller. “Die Saurier der Unteren Dyas von Sachsen.” Palceontogr. xxix. 1882, p. 1.—A. Gaubry. Les Bnchainements du Monde animal dans les temps geologigues. Fossiles privxaires (Paris : 1883, 8vo), p. 251.—E. D. Cope. “The Batrachia of the Permian Period of North America.” Amer. Nat. xviii. 1884, p. 26.—E. Fraas. “Die Labyrinthodonten der Schwabischen Trias.” Palceontogr. xxxvi. 1889, p. 1.—L. v. Ammon. Die Permischen Amphibien der Rheinpfalz. Munich : 1889 (1891), 4to.—R. Lybekker. Catalogue of the Fossil Reptilia and Amphibia in the British Museum. Part IV London: 1890, 8vo.—E. Fraas. Die Schwdbischen TriasSaurier nach dem Material der K. Natwalien-Sammlung in Stuttgart zusammengestellt. Stuttgart: 1896, 4to..— O. Jaekel, “Die Organization von Archegosaurus." Zeitschr. Deutsch. Geol. Ges. xlviii. 1896, p. 505.—F. Broili. “Ein Beitrag zur Kenntniss von Eryops megacephalus.” Palceontogr. xlvi. 1899, p. 61. (10) “Amphibian Footprints from the Devonian.” Amer. Journ. Sci. ii. 1896, p. 374. (ID “Decouverte du plus ancien Amphibien connu. . . . dans le Famennien superieur de Modave.” Bull. Soc. Beige Geol. xv. 1888, p. cxx. (12) “A Batrachian Armadillo.” Amer. Nat. xxix. 1895, p. 998. (13) C. Gegenbaur. Entersuchungen zur vergleichenden Anatomie der Wirbelsdule bei Amphibien und Reptilien. Leipzig: 1862, 4to.—H. Gabow. “On the Evolution of the Vertebral Column of Amphibia and Amniota.” Phil. Trans, clxxxvii. B. 1896, p. 1. (14) R. Wiebersheim. Die Anatomie der Gymnophionen. Jena, 1879, 4to. W. Peters. “Ueber die Eintheilung der Caecilien.” Mon. Berl. Ac. 1879, p. 924.—G. A. Boulenger. Catalogue of Batrachia Gradientia s. Caudata and Batrachia Apoda in the Collection of the British Museum. London : 1882, 8vo, and “ A Synopsis of the Genera and Species of Apodal Batrachians.” P. Z. S. 1895, p. 401. (15) “On the Structure and Affinities oiChe Amphiumidce." Proc. Amer. Philos. Soc. xxiii. 1886, p. 442. (16) Ergebnissenaturwissenschaftlicher Forschungen auf Ceylon, II. Wiesbaden : 1887-90, 4to. (17) “ The Chondrocranium of the Ichthyopsida.” Stud. Biol. Lab. Tufts Coll. No. 5, 1898, p. 147. (18) G. A. Boulenger. Catalogue, t. c. 1882. (19) H. H. Wilber. “ Lungenlose Salamandriden.” Anat. Anz. ix. 1894, p. 216.—L. Camerano. “Ricerche anatomofisiologiche intorno ai Salamandridi normalmente apneumoni.” Atti Acc. Torin. xxix. 1894, p. 705, and xxxi. 1896, p. 512.—H. H. Wilber. “ Lungless Salamanders.” Anat. Anz. xii. 1896, p. 182.— E. Loennberg. “Notes on Tailed Batraehians without Lungs,” Zool. Anz. xix. 1896, p. 33. (20) “Note sur le Batracien de Bernissart.” Bull. Mus. Belg. iii. 1884, p. 85. (21) G. A. Boulenger. Catalogue of Batrachia Salientia s. Ecaudata in the Collection of the British Museum. London: 1882, 8vo. (22) “ On the Development of the Vertebral Column in Pipa and Xenopus.” Anat. Anz. xiii. 1898, p.359. (23) G. A. Boulenger. “ On Hymenochirus, a New Type of Aglossal Batrachians.” Ann. and Mag. N. II. (7) iv. 1899, p. 122. —W. G. Ribewood. “ On the Hyobranchial Skeleton and Larynx of the New Aglossal Toad, Hymenochirus boettgeri.” J. Linn. Soc. xxvii. 1900, p. 454. (24) W. Wolterstorff. “Ueber fossile Frosche, insbesondere Palceobatrachus.” Jahresb. Nat. Ver. Magdeb. 1885 and 1886. (25) W. Peters. “Ueber die Entwickelung eines Batrachiers, Hylodes martinicensis, ohne Metamorphose.” Mon. Berl. Ac. 1876, p. 709.—A. Kappler. “ Die Tierwelt in Hollandischen Guiana.” Das Ausland, 1885, p. 358. G. A. Boulenger. “Reptiles and Batrachians of the Solomon Islands.” Trans. Zool. Soc. xii. 1886, p. 51.—H. v. Ihering. “ On the Oviposition of Phyllomedusa iheringii.” Ann. and Mag. N. II. (5) xvii. 1886, p. 461.—H. H. Smith. “ On Oviposition and Nursing in the Batrachian genus Dendrobates.” Amer. Nat. xxi. 1887, p. 307.—G. B. Howes. “Notes on the Gular Brood-pouch of Rhinoderma darwini.” P. Z. S. 1888, p. 231.—W. J. Hollanb. “Arboreal Tadpoles.” Amer. Nat. xxiii. 1889, p. 383.—E. A. Goelbi. “Contribution to the Knowledge of the Breeding Habits of some Tree-frogs of the Serra dos Orgaos, Rio de Janeiro, Brazil.” P. Z. S. 1895, p. 89.—G. A. Boulenger. “On the Nursing Habits of two South American Frogs.” P. Z. S. 1895, p. 209.—A. Brauer. “Einneuer Fall von Brutpflege bei Frdschen.” Zocl. Jahrb. Syst. xi. 1898, p. 89.—S. Ikeba. “ Notes on the Breeding Habit and Deeo^vaevA of Rhacophorus schlegelii.” Annot. Zool. Japan, i. 1898, p. 113. (g. A. B.) Amphioxus.—Amphioxus has been briefly treated under the headings Ichthyology, Lancelet, and Vertebrata in the ninth edition of this work. Such, however, is its importance in the present zoological system that a more extended notice is desirable. The theoretical interest of Amphioxus depends upon a variety of circumstances. In its manner of development from the egg, and in the constitution of its digestive, vascular, respiratory (branchial), excretory, skeletal, nervous, and muscular systems it exhibits what appears to be a primordial condition of vertebrate organization, a condition which is, in fact,