1024 CLASS AMPHIBIA. 



to 70 mm., these larvae cast their gills, and became air-breathers ; their 

 development being thus analogous to that of the existing Salamanders. 

 The adults measure from 100 to 160 mm. In the course of the meta- 

 morphosis the skull decreases somewhat in width, and the thoracic 

 buckler grows much more rapidly than the scapula and coracoid, while, 

 curiously enough, the pelvis shifts its position, and thus increases the 

 number of presacral vertebrae from 20 to 26. In the larva the under- 

 side of the body is naked (fig. 953), but in the adult there is a complete 

 armour of bony scutes on this aspect. 



Other genera of which some may perhaps be included in this 

 family are Amphibamus, from the Carboniferous of Illinois ; Peliott, 

 from that of Ohio ; Batrachiderpeton, from the Carboniferous of 

 Britain ; Hylerpeton, from that of Nova Scotia ; Dawsonia, from 

 the Permian of Bohemia; and Sparodus, from the latter deposits. 

 Batrachiderpeton is remarkable for the absence of maxillary teeth, 

 and the clustering of the palato-vomerine teeth ; Sparodus present- 

 ing the latter feature, but retaining the maxillary teeth. The pala- 

 tines of the latter genus are splint-like bones interposed between the 

 vomers and maxillae. 



Family Apateonid^e. — In this family the skull (fig. 954) is tri- 

 angular and comparatively narrow, while the teeth are marked by 

 small grooves at their summits. The type genus Apateon is found 

 in the Carboniferous rocks of Germany, while the allied Melanerpeton 

 is from the Permian of Bohemia. An enlarged view of the dorsal 

 aspect of the skull of the latter genus is shown in fig. 954, the reten- 

 tion of the internal gills indicating that it belonged to an immature 

 individual. 



Suborder 2. Aistopoda. — In this remarkable group the body 

 has a snake-like form, with well-developed ribs, but probably with- 

 out either pectoral or pelvic girdles or limbs. The teeth are not 

 folded ; and Dr Fritsch considers that the external gills persisted 

 throughout life. 



Family Dolichosomatid^e. — This family, which is equivalent to 

 both the Plegothonidce, and Molgophidce of Professor Cope, is repre- 

 sented in the Carboniferous of Britain and the Permian of Bohemia 

 by Dolichosoma and Ophiderpeton. In the former the skull is long 

 and narrow, with no sculpture on the bones, and it is probable that 

 the body was entirely naked ; but in the latter the skull may have 

 been shorter, and there was an armour on both surfaces of the 

 body, the scutes on the ventral side being long oat-like splints, 

 while those on the back were rounded and shagreen-like. The 

 ossified gill-supports were furnished with small enamel-like denti- 

 cules. One of the species of Dolichosoma attained a length of about 

 two feet. Plegethontia and Molgophis, from the Carboniferous of 

 Ohio, appear to be nearly related. Palceosiren, from the Permian 

 of Bohemia, is a gigantic form provisionally included in this family, 



