Extinct, salamander-like amphibians, with broad, obtusely rounded cranium; external branchiæ present in young; sclerotic plates present; bones of the cranium not ornamented with deep pits and grooves nor cut by the lateral-line canals, though sometimes ornamented with slight scorbiculations; notochord always persistent; vertebræ cartilaginous (in caudal region) or but partially ossified, the ossification being entirely perichondral; a single sacral vertebra; transverse process of vertebræ large in dorsal region; ribs always short, straight, and heavy, present throughout the length of the vertebral column and borne on the transverse processes centrally; caudal region of moderate length with elongate fleshy tail; usually 20 presacrals, of which 4 or 5 may be considered cervicals; limbs natatory and always present, well developed; elements of the appendicular skeleton composed entirely of perichondrium; carpus and tarsus cartilaginous; digits 4 in the hand and 5 in the foot; phalangeal formula for the hand usually 2-2-3-2 and for the foot 2-3-4-3-2; distal phalanges not clawed; abdomen covered with closely packed corneous scutes or scales; body naked or covered with minute horny scales; median and dorsal lateral lines present on the posterior part of body and on tail. CHAPTER IX. THE AMERICAN COAL MEASURES BRANCHIOSAURIDÆ. Definition Op the Family Branchiosauridæ Fritsch, 1879. Coal Measures and Permian Op North America and Europe. Fritsch, Fauna der Gaskohle, Bd. I, p. 69, fig. 30, 1879. Lydekker, Cat. Fossil Reptilia and Amphibia, pt. IV, p. 210, 1890 (Protritonidæ;). Stegocephalic, salamander-like animals, with broad, anteriorly truncate skull. Teeth smooth with large pulp-cavity. The parasphenoid narrowed anteriorly, posteriorly expanded to a shield-shaped plate. Vertebra; with the notochord persistent and intravertebrally expanded. Pelvis well developed, the ilium and ischium osseous with large cartilaginous margins, the pubis unknown, possibly hyaline cartilage. Ribs short, straight, present on almost all vertebræ. Skin with delicately ornamented scales. Eyes with sclerotic plates. Palatal elements toothless or with small tooth-like tubercles on pterygoids and palatines. Ventral armature on throat, chest, and abdomen, extending on to the limbs, consisting of small delicate scutellæ arranged in a chevron pattern. The above definition is modified from Fritsch (Fauna der Gaskohle, Bd. I, p. 69, 1879). The North American species are: (?) _Sparodus_ sp. indet. Dawson, _Micrerpeton caudatum_ Moodie, _Mazonerpeton longicaudatum_ Moodie, _Mazonerpeton costatum_ Moodie, _Eumicrerpeton parvum_ Moodie. =Genus MICRERPETON Moodie.= Moodie, Jour. Geol., 17, p. 39, figs. 1 to 6, 1909. Type _Micrerpeton caudatum_ Moodie.