6 
is a massive plate, the ends of which are produced in opposite directions ; 
the one into a massive shorter prominence ; the other longer and plate-like. 
Between these prolongations, the inferior edge of the bone bears a single 
row of well developed teeth. The patch of small teeth first described, 
commences at the extremity from which the longest process rises on the 
opposite side of the series of large teeth. This Z-shaped bone is, from its 
massive character, generally preserved, and I was long familiar with it, 
before I could refer it to its position. In one specimen, a part of it bearing 
teeth, adheres to the upper jaw at the diastema. 
The posterior part of the skull of one of the specimens above mentioned 
displays typical reptilian characters. The occipital condyle is not perforated, 
nor divided by sutures. The exoccipital bones project well backwards. 
The lateral walls of the brain-case are massive as far forward as the exit 
of the fifth pair of nerves ; anterior to this point they were thin or want- 
ing. The basisphenoid carries two parallel descending lamin, which 
bound a deep median fissure, and then unite anteriorly. Posteriorly they 
abut on a descending process, which is followed by a lid-like element 
which is applied to a circular fossa with a raised border near the occipital 
~ condyle. 
The articular face of the articular bone of the mandible consists of two 
parallel cotyli, divided by a ridge of articular surface. This part of the 
jaw is much depressed, as in Hryops. The large teeth of the lower jaw are 
at the anterior extremity. 
_The neural spine of the axis is flat and elongate antero-posteriorly. 
From this point the neural spines rise rapidly in elevation until on the 
dorsal region they are many times as long as the diameters of the centra. 
The latter are not very unequal in their proportions in different parts of the 
column. Those from the posterior regions are less compressed than the 
dorsals and cervicals. The dorsals are separated by intercentra below, 
which are small in the D. cncistvus, and larger in the D. gigas. All the 
ribs are two-headed, commencing with the axis. All the crevical and dor- 
sal vertebre have diapophyses with tubercular facets. The head of the 
rib is prolonged downwards and forwards to the prominent border of the 
anterior articular face, against which it abuts, but so far as yet observed, 
without a corresponding facet. On the caudal vertebre the two facets of 
the ribs are approximated and finally are not distinguished. They are here 
coossified with the centra. : 
The humerus accompanying one of the specimens of D. incistvus, is of 
the form No. 3, of my description of humeri in the Paleontological Bulle- 
tin No. 29, p. 528. The extremities are expanded and the shaft is without 
diagonal ridge ; the supracondylar foramen is enclosed, and the condyles are 
robust. The pelvis of the D. gigas is in general like that of Clepsydrops natalie 
(1. ¢., p.510). The elements are codssified, but the ischiopubic syinphysisis not 
so deep as in the Butrachia of the same beds. The ilium is shortened above, 
and its direction is at right angles to the long axis of the inferior elements 
The foramen of the internal femoral artery is distinct. The femur of the 
