CLASS BATRACHIA. Sub-Class I. STEGOCEPHALI. Order 1. Ganocephali: _Trimerorhachis_, _Archegosaurus_. 2. Rhachitomi: _Eryops_. 3. Embolomeri: _Cricotus_. 4. Microsauri: _Branchiosaurus_, _Hylonomus_, etc. {10} Sub-Class II. URODELA. Order 1. Proteidae: _Proteus_. 2. Pseudosauria. [All the rest of the Urodela + Coeciliidae.] 3. Trachystomata: Sirenidae. Sub-Class III. SALIENTIA. P. and F. Sarasin, 1890, "Zur Entwicklungsgeschichte der Ceylonesischen Blindwühle, Ichthyophis glutinosa."[10] Sub-Class I. ARCHAEOBATRACHI s. STEGOCEPHALI. II. NEOBATRACHI. Order 1. _URODELA._ _a_. Salamandroidea. [The Urodela.] _b_. Coeciloidea = Amphiumidae + Coeciliidae. 2. _ANURA._ The classification adopted in this volume is as follows:– CLASS AMPHIBIA. Sub-Class I. Phractamphibia. Order I. Stegocephali Lepospondyli. Sub-order 1. Branchiosauri. Sub-order 2. Aistopodes. Order II. Stegocephali Temnospondyli. Order III. Stegocephali Stereospondyli. Sub-Class II. Lissamphibia. Order I. Apoda. Order II. Urodela. Order III. Anura. Sub-order 1. Aglossa. Sub-order 2. Phaneroglossa. {11}CHAPTER II SKELETON OF URODELA AND ANURA–SKIN–COLOUR-CHANGING MECHANISM– POISON-GLANDS–SPINAL NERVES–RESPIRATORY ORGANS–SUPPRESSION OF LUNGS– URINO-GENITAL ORGANS–FECUNDATION–NURSING HABITS–DEVELOPMENT AND METAMORPHOSIS SKELETON OF THE URODELA THE VERTEBRAL COLUMN.–The number of vertebrae is smallest in the terrestrial, greatest in the entirely aquatic forms, and is exceptionally large in the eel-shaped _Amphiuma_. In the following table the sacral vertebra is included in those of the trunk. Trunk. Tail. _Siren lacertina_ 22 35 + _Necturus maculatus_ 19 29 _Proteus anguinus_ 30 28 + _Cryptobranchus alleghaniensis_ 20 or 21 24 + _C. scheuchzeri_ 21 _C. japonicus_ 22 22 to 26 _Amphiuma means_ 63 35 + _Amblystoma tigrinum_ 17 or 16 32 + _Salamandra maculosa_ 17 27 _Triton cristatus_ 17 36 _Triton taeniatus_ 14 or 15 36 + _Triton palmatus_ 14 23 to 25 _Salamandrina perspicillata_ 15 32 to 42 _Spelerpes fuscus_ 16 23