Reports and Proceedings — Geological Society of London. 281 



evidence, to conceive of their being referred to different classes of 

 animals." 



" But if the order Labyrinthodoutia is transferred to the Eeptilia, 

 it is then manifest that by including such genera as Branchiosaurus 

 and Archegosaurus, in which gill-arches are found, it introduces into 

 the Eeptilia a character hitherto unknown, and commonly regarded 

 as Amphibian. ... If the osteology of an ordinal type is 

 Reptilian, it cannot be placed in the Amphibia, because two or 

 three genera, or the whole group, preserve gill-arches. . . . The 

 Labyrinthodoutia may or may not be a homogeneous sub-class or 

 order, though the circumstance that many writers have separated 

 its groups on different principles, and into a varying number of 

 orders, is some evidence that it includes a wide range in character. 

 . . . In no part of the skeleton is there a close correspondence 

 between living Amphibia, which are probably unknown before the 

 Tertiary period, and the extinct Labyrinthodoutia, which are only 

 known with certainty in the Carboniferous, Permian, and Triassio 

 periods of time." 



" If the sub-orders of Labyrinthodoutia are sub-orders of Eeptilia 

 and not of Amphibia, the transition which Fareiasaurus exhibits 

 from Labyrinthodonts to Mammals ceases to be an anomaly." 



" The close resemblance of form of the bones in the several parts 

 of the skeleton now described with Monotremata and Anomodontia 

 makes the border-line between Eeptiles and Mammals more difficult 

 to define." 



The fossil is identified as an Anomodont reptile, chiefly on the 

 basis of resemblance to Procolophon and Pareiasatirus. It is shown 

 not to be a mammal by the large parietal foramen, the composite 

 structure of the lower jaw, and the presence of the pre-frontal bone. 

 It difli'ers from known Anomodonts in making a somewhat closer 

 approximation to Monotreme mammals than has hitherto been 

 evident, and this correspondence extends to successive segments of 

 both the fore- and hind-limbs. 



The teeth are in sockets placed obliquely, with conical crowns 

 compressed to sharp lateral margins, and curved inward. The 

 proportions of the vertebral column are those of Echidna, though 

 the transverse processes are longer, as in Fareiasaurus. The ribs 

 are like those of a Monotreme, though the sacral ribs are longer. 

 The shoulder-girdle resembles that of Frocolophon, and differs from 

 typical Anomodonts in the constituent bones being unanchylosed, 

 and in the pre-coracoid having a large anterior extension in advance 

 of the scapula. The sternum appears to have been unossified, as in 

 Crocodilia. The humerus is widely expanded at both extremities 

 and twisted, but does not show the peculiar lateral curvature seen 

 in Monotremes. The ulna gives no evidence of an olecranon- 

 process ; it is larger than the radius, and appears to articulate with 

 the humerus. The pelvic bones are without acetabular or obturator 

 perforations, are not anchylosed together, and the ilium is not 

 expanded transversely. The hind-limb is no larger than the fore- 

 limb. The femur is more slender than the similar bone in Echidna. 

 The fibula is prolonged proximally beyond the stout tibia round 



