Geological Society. 481 
PROCEEDINGS OF LEARNED SOCIETIES. 
GEOLOGICAL SOCIETY. 
March 22, 1884.—Prof. T. G. Bonney, D.Sc., F.R.S., 
President, in the Chair. 
The following communications were read :— 
1. “ On Rhytidosteus capensis, Owen, a Labyrinthodont Amphibian 
from the Trias of the Cape of Good Hope.” By Sir Richard Owen, 
eC 5: EE... B.G.S. 
The author first noticed the discovery of certain forms of Am- 
phibia belonging to the genera Labyrinthodon, Brachyops, Petrophryne, 
and Lhinosaurus, and called attention to certain typical peculiarities 
in the structure of the teeth, the form of the bony palate, and the 
double occipital condyle. 
An imperfect cranium of the species now described as Rhytid- 
osteus capensis was procured by Heer Swanepoel from the Trias on 
his farm of Beersheba, in the Orange Free State, and deposited by 
him in the Bloemfontein Museum. 
This specimen, which was brought to England and submitted to 
the author by Dr. Exton, consists of the anterior portion of the 
skull with part of the mandible attached. The general form is 
batrachoid, and one of the hinder palato-vomerine teeth, on being 
examined microscopically, exhibited the characteristic labyrinthodont 
structure. 
The surface of the skull, and the characters of the premaxillary, 
nasal, frontal, and prefrontal bones were described. ‘The parietals 
and postfrontals are imperfect, the hinder part being lost. The 
rami of the mandible are also imperfect behind, but a broken frag- 
ment shows the articular surface. The vomerine bones were also 
described, with the posterior nostril and the teeth before and behind 
this opening. The breadth of the bony palate at its hinder frac- 
tured border is 5 inches ; the length of the part preserved 43 inches ; 
the mandible, when perfect, was probably from 11 inches to a foot 
in length. The author also gave an account of the dentition wielded 
by the premaxillary, maxillary, vomerine, palatine, and mandibular 
bones. 
The author pointed out that the type of air-breathing vertebrates 
to which the present genus belongs reached its highest development 
in the Triassic period in Britain, Russia, North America, Hindostan, 
and South Africa. The only known antecedent form from which 
the labyrinthodont structure of tooth might have been derived is a 
genus of fishes named Dendrodus, in the Old Red Sandstone. The 
Liassic Ichthyosaurs also show some similarity in tooth-structure ; 
but in them there is far greater simplicity. 
