CHAPTER VIII. 



DEFINITION OF THE CLASS AMPHIBIA L1NNE', 1758, DEVONIAN TO RECENT. 



(World-wide distribution.) 



Cold-blooded vertebrates; aquatic or partially terrestrial in habit; body scaled or naked or 

 partly covered with bony or horny plates; abdomen sometimes protected by closely packed scutes, 

 scales, or rods ; skull completely roofed over or with a single vacuity ; pterygoid-palatine arch complete 

 or wanting ; stapes always present ; two occipital condyles, sometimes cartilaginous ; skull bones pitted 

 and grooved by the lateral-line canals, or smooth and lateral-line canals wanting; parasphenoid 

 well developed ; palatine vacuities, large, small, or absent ; basioccipital partly or entirely cartilaginous; 

 sclerotic plates present or absent ; mouth always terminal ; teeth sharply conical, smooth, or plicated, with 

 walls sometimes extremely complicated by the infolding of the dentine and enamel. Vertebras procoelous, 

 opisthoccelous, amphicoelous, amphiplatyan, temnospondylous, stereospondylous, or cartilaginous; 

 notochord often persistent ; column divisible into cervical, dorsal, and caudal series ; cervical series, so far 

 as known, always short; dorsal region long or short; a single sacral or two; caudal series short, very long, 

 or absent. Pectoral girdle composed of an osseous scapula, cleithrum, clavicle, interclavicle, and 

 coracoid with various relations ; sternum undeveloped ; pectoral girdle of membrane bones ; in Triassic 

 forms producing the effect of a plastron on account of the high development of the clavicles and inter- 

 clavicle. Pelvis usually composed of an osseous ilium and ischium; pubis when osseous surrounded 

 by large amounts of cartilage, usually cartilaginous, sometimes calcified. Limbs ambulatory, nata- 

 tory, or wanting ; limb bones composed either entirely of perichondrium or of perichondrium and a 

 small amount of endochondrium ; radius and ulna, and tibia and fibula free or fused. Digits 3 to 5, 

 usually 4 for the hand and 5 for the foot. Terminal phalanges sometimes clawed. Carpus and tarsus 

 osseous or cartilaginous, usually the latter. Ribs never attached to a sternal apparatus, single or 

 double headed or intermediate, long and curved or short and straight. Articulation with vertebral 

 column inter- or intra-central. Respiration both branchial and pulmonary ; branchiae persistent and 

 osseous in some forms. Development by metamorphosis either in the egg membrane, on the back of 

 the mother, or in the water. No amnion or allantois. Heart with a single ventricle and 3 or 4 pairs 

 of aortic arches; postcava always present in the recent forms. 



DEFINITION OF SUBCLASS EUAMPHIBIA, MOODIE, 1909. COAL MEASURES 



TO RECENT. 



(World-wide distribution.) 



MOODIE, Trans. Kans. Acad. Sci., 1909, p. 243. 



MOODIE, Geol. Mag., n. s., Dec. v, vol. vi, p. 220, May, 1909. 



The present group was established for the reception of the Branchiosauria and 

 their descendants, the Caudata, with the related forms, the Apoda. The Salientia 

 are included provisionally, since there is no evidence of the origin or relationship 

 of this group of animals to other Euamphibia save that they have attained the 

 same stage of evolution. They arc in no way closely related to any known group 

 of Amphibia, recent or extinct, but they stand on the same plane of development 

 as the Caudata and present similar structures, i.e., a single ventricle in the heart, 

 external branchiae in the young, a glandular skin, perichondral bone, and a large 

 parasphenoid. The origin of the Salientia is a puzzle and must remain so until 

 further paleontological evidence is forthcoming. Wyman, Cope, and the writer 

 have all remarked on the similarity of structure between the Salientia and 

 single known specimen of Pel-ion lyelli Wyman from the Linton, Ohio, Coal Measures. 



49 



