SIR R. OWEN ON A LABYRINTHODONT AMPHIBIAN. O07 
includes the splenial (31) with the dentary (32) elements: the former 
enters into the composition of the hind part of the symphysis man- 
dibulez. The ramus so constituted has the form of a stout bony 
bar, the vertical and transverse diameters being subequal, and the 
under part thick and convex across. Hach ramus is slightly bent 
outwards as it diverges from the symphysis: its outer surface is 
sculptured in a pattern similar to that of the skull-bones. 
A detached hinder end of one of the ramishows the articular surface, 
29 (Plates XVI. & XVII.), divided into a transverse pair of shallow 
concavities. The part of the ramus supporting these seems also to 
have developed, as in Crocodilia, the angular projection (Plate XVI. 
fig. 1, 29) behind the joint 29’, for the tympanic. ‘There is a trace 
of suture which bounded the angular element, also of the croco- 
dilian pattern. If the mandibular fossil above noticed had been 
found unassociated with other bones of the skull, its reference to a 
saurian might be condoned. The extreme depth or vertical diame- 
ter of this detached hind end of the mandibular ramus of Hhytidosteus 
is 60 millim., its greatest diameter 48 millim. 
Some lost portion of the ramus prevents a close fit of the above 
portion with the dentigerous part adhering to the upper jaw; but 
the entire length of the lower jaw may be fairly estimated at from 
11 inches to a foot. 
Dentition.—This armature is wielded by the premaxillary, vome- 
rine, partly palatine, and mandibular bones. In each premaxilla a 
single row of from eight to ten small, pointed, conical teeth extend 
along the alveolar border (Plate XVI. fig. 2, 22; and Plate XVII. 
fig. 1, 22), to wheré the crowns of two large teeth, which may be 
called ‘‘canines” (Plate XVI. fig. 1), project from the maxilla. Beyond 
these a row of teeth, smaller than those of the premaxillary series, 
extends along the margin of the maxilla to near the orbit. The 
corresponding mandibular teeth, in the small degree in which they 
could be exposed, correspond in shape, size, and number, with the 
maxillary series. The chief weapons of the present labyrinthodont 
genus are supplied by the vomerine and palato-vomerine pairs of 
laniariform teeth. From one of the latter was taken the section 
affording the subject of the drawing (Plate XVII. fig. 2). 
Should the present communication be favoured, like that of a 
British Triassic labyrinthodont, read before the Geological Society 
in 1840, with illustrations of the natural size, such as those which 
appeared in plates 43-47, vol. vi., of the then quarto form of our 
publications, the acquisition by the estimable individuals and 
Societies in our Cape Colony, of further evidences of Rhytidosicus 
capensis may be aided and stimulated by such figures accompanying 
the description of the present Triassic anallantoid reptile*. 
Tt would seem that at this geological period, in parts of our 
elobe so remote from each other as Britain, Russia, North America, 
* Since writing the above, I have found that a reduction of one third would 
bring the requisite illustrations within the 8vo form, and probably serve the 
same purpose. 
