1889.] OF A THERIODONT REPTILE. 575 
the Monotremes, it is evident that the process marked ain Plate LV. 
also represents the same. Further it is manifest that the process 4 
is the distal extremity of part of the preaxial border of the scapula, 
which has become twisted from the line of the acromion towards the 
dorsal aspect, this being most marked in Ptychosiagum (fig. 2). 
This dorsal torsion of the preaxial border of the scapula is a very 
remarkable feature, and appears to support Professor Flower’s view 
that the preaxial border of the Monotreme scapula represents the 
spine of the scapula of the higher Mammals. Thus in the scapula 
of Ptychosiagum the body of the bone has become to a great extent 
three-sided, and the surface on the inner side of the preaxial border 
would well represent the prescapular fossa of the higher mammals, 
the portion on the outer side of the same the postscapular fossa, 
and the somewhat rounded posterior surface (left side of figure) the 
subscapular fossa. If, as seems most probable, we really have in 
this type of scapula an indication how the reptilian scapula of the 
Monotremes was modified into that of the higher mammals, and 
the acromion is rightly identified, we shall further have to assume 
that the acromial process also subsequently received a dorsal torsion, 
so as to resume its original position at the distal extremity of the 
preaxial border, now converted into the spine. 
After this long digression it will suffice to add that the scapula of 
the form under consideration corresponds very closely to that 
described as Platypodosaurus. 
The humerus is represented by the somewhat imperfect distal 
half of that of the left side, a restored figure of which is given in 
Plate LV. fig. 3, on a scale of one third. This specimen shows the 
entepicondylar foramen underlying a bar situated in the usual position 
on the palmar aspect of the shaft. The radial condyle is large and 
well preserved, and above this there is the supinator flange on the 
preaxial border which serves to distinguish the humerus of the 
Theriodonts from that of the Dicynodonts. Unfortunately, however, 
this flange is imperfect, so that it cannot be determined whether 
there was an ectepicondylar foramen. 
Compared with the. Anomodont humeri in the British Museum 
this specimen agrees very closely, both in size and contour, with the 
cast of the corresponding portion of a left humerus from the Permian 
of Russia described under the name of Brithopus*. The Russian 
specimen (Plate LV. fig. 4) has been a good deal damaged, and its 
radial condyle has been broken away ; but allowing for this imperfec- 
tion the general resemblance between the two specimens is very close. 
Trusting to this resemblance in the distal extremities of the two 
humeri the proximal extremity of the African bone has been restored, 
partly from a Russian specimen doubtless referable to Brithopus*, and 
partly from the large African humerus figured in pl. xii. of Owen’s 
‘Catalogue,’ as Pariasaurus, but which more probably belongs to 
Tapinocephalus. The present specimen appears to be distinguished 
1 For synonymy, see Owen, Quart. Journ. Geol. Soc. vol. xxxii. p. 352 
et seq. 
2 Vide Owen, loc. cit. 
