ORDER I STEGOCEPHALIA 125 



several distinct series. Those of the thoracic region form transverse rows ; those of 

 the pectoral region oblique rows converging posteriorly toward the median line ; 

 those of the abdominal region oblique rows, converging at a lesser angle in the opposite 

 direction ; and those of the under side of the tail and legs form slightly curved trans- 

 verse rows. Functional gill arches are indicated in many immature examples by the 

 regulär series of minute denticles which were originally arranged on them. Tail 

 known to have been about as long as trunk wdth the head, but most of the caudals 

 unossified. 



This genus and Archegosaurus furnish the commonest and best known examples 

 of Palaeozoic Amphibians. Eemains of Branchiosaurus are abundant in the fine- 

 grained limestone of the middle Eothliegendes, near Dresden, where the small bones 

 are clearly outlined in wählte against a grayish-coloured matrix. Credner's elaborate 

 researches on the strueture and development of this form w^ere based on comparisons 

 of over 1000 specimens. Several species occur also in the Lower Permian of Nürschan 

 (Nyran) and Kunova in Bohemia, and Oberhof and Friedrichsroda in Thuringia. 



Pelosaurus, Credner (Fig. 193, d). 18 to 20 cm. long. Skull relatively very 

 large, with lachrymal in front of orbits, and no supplementary sclerotic plates. 

 Lower Permian ; Niederhässlich, near Dresden. F. laticeps, Credner. 



Melanerpeton, Fritsch (Figs. 200, 205, h). 2*5 to 13 cm. long. Skull as in 

 Branchiosaurus, but more produced posteriorly, and squamosal divided (5^ and 

 x). Interclavicle extended into a long posterior process. A distinct dermal 

 armouring not present, but quantities of small calcareous shagreen-like 

 particles sometimes observed instead. Branchial arches present in young 

 examples. Lower Permian of Braunau, Bohemia ; Lhotka, Moravia ; and 

 Niederhässlich, Saxony. 



Dawsonia, Fritsch. Jaw- bones, vomer, palatines, and parasphenoid 

 armed with teeth. Lower Permian ; Bohemia. 



Amphibamus, Cope ; Pelion, Wyman. Goal Measures ; Linton, Ohio. 



Sub-Order B. LEPOSPONDYLI. Zittel. {Microsauria. ) 



Notochord persistent and enclosed in constricted hony cylinders^ hourglass-shaped 

 in longitudinal section. Teeth simple, conical, hollow. 



Family 1. Microsauridae. Dawson. 



Salamander or lizard-like, usually longicaudate Stegocephalia. Fore-limbs less 

 robust than the hinder pair, carpus and tarsus ossified or cartilaginous. Eibs long 

 and slender, curved, generally double -headed. Pubis ossified. 

 Ventral, and in rare cases also the dorsal surface covered with 

 small, round, oblong, oval or oat-shaped scales. Carboniferous 

 and Permian. 



^ Hyloplesion, Fritsch. Cranial bones smooth, finely striated 

 or punctate. Orbits large, with sclerotic ring. Tarsus ossified. 

 According to Fritsch, both dorsal and ventral armatures were 

 present, composed of overlapping oval scales with thickened 

 posterior border. Lower Permian: Nürschan, Bohemia, and ^ vertebra, and 



tj^ T 1 c< B,R\hofHylononuts 



Niederhässlich, Saxony. lyeiH, Dawson. coai 



Hylonomus, Dawson (Fig. 209). Small and imperfectly ^"scot'ia"!'^^'"'' 

 known, perhaps identical with the preceding. Coal Measures ; 

 Nova Scotia. Other allied American genera are Amhlyodon, Dawson ; 



