164 LABYRINTHODONTIA. 



much compressed laterally, straight, smooth, with very prominent 

 fore-and-aft carinas * ; a large pulp-cavity, and the dentine much 

 folded. Cranial sculpture pitted, and extending over all the bones. 

 Mandibular rami slender. Vertebral column with very large inter- 

 centra, which carry the chevrons in the caudal region. 



Orthosaurus and Megalocephalus were founded on the evidence of 

 imperfect crania, and Macrosaurus on a portion of the vertebral 

 column ; all being apparently referable to the type species. The 

 vertebral column on which Macrosaurus was based is described and 

 figured by Embleton in ' Nat. Hist. Trans. Northumb. & Durham,' 

 vol. viii. p. 349, pi. vi., and referred to Loxomma. The large inter- 

 centra are well shown, and approximate to those of the embolome- 

 rous type. 



Loxomma allmani, Huxley 2 . 



Syn. Orthosaurus pachycephalias, Barkas 3 . 



Macrosaurus polyspondylus, Barkas 4 . 



- Meg otocephalus macromma, Barkas 5 . 



The type species. Skull vaulted, with a broad and somewhat 

 spatulate muzzle ; total length usually about 0,333 (13*5 inches), 

 length in middle line 0,291 {IV b inches) ; greatest width 0,227 

 (9 inches). Crowns of teeth not serrated. 



A skull is figured by Embleton and Atthey in the ' Ann. Mag. Nat. 

 Hist.' ser. 4, vol. xiv. pis. iv.-viii. (1874); the skulls figured by 

 Barkas are crushed flat, and therefore appear larger. The type 

 specimen is from the Lower Carboniferous ironstone of Gilmerton 6 , 

 near Edinburgh ; an horizon probably corresponding to the uppe r 

 part of the Mountain Limestone of England. 



Hah. Europe (Britain). 



R. 585. The cranium, wanting the greater part of the inferior 

 (Fig.) moiety of the mandible ; from an ironstone band in the 

 Coal-Measures (Upper Carboniferous) of Dawley, near 

 Coalbrookdale, Shropshire. This specimen is the only 

 known European Labyrinthodont in which the contour of 

 the skull is completely preserved ; the restored figure 



1 In the Permian L. bohemicum, Fritsch (Fauna der Gaskohle, vol. ii. pt. i. 

 p. 10, pi. lviii., 1885), the carina? are serrated. 



- Quart. Journ. Geol. Soc. vol. xviii. p. 293 (1862). 



3 Coal-Measure Palaeontology, p. 61, pi. viii. (1873). 



1 Ibid. p. 58, pi. vii. 



5 Ibid. p. 69, pi. ix. fig. 189. In description incorrectly given as pi. viii. 



G See Quart. Journ. Geol. Soc. vol. xix. p. 56, note. 



