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1004 MR. D. M. 8S. WATSON ON 
' 
difference, but one which the example of the Chelonia teaches us 
might have occurred very rapidly. 
The vertebral column of Broomia is very similar to that of the 
Captorhinids, having small completely perforated centra, heavy 
neural arches and horizontal zygapophysial articulations, and 
small intercentra. The rib articulations, however, are smaller in 
our type. 
The limb-girdles of Broomia are totally unlike those of any 
Cotylosaur in their great slenderness. The shoulder-girdle differs 
very markedly from that of the Captorhinide, but faintly recalls 
that of Seymouria in its peculiar interclavicle with a diamond- 
shaped head and in the clavicle with its curious expanded lower 
end. The loss of the posterior coracoidal element is paralleled 
by Seymouria, but in that type if I interpret Prof. Williston’s 
description accurately, the real Coracoid was present although it 
was not ossified and contributed to the glenoid cavity, which, as 
in the majority of Carboniferous reptiles, had the peculiar screw- 
shaped form most typically shown in Diadectes and Hryops. 
Traces of this former possession of this type of glenoid cavity are 
to be seen in Broomia, but the conditions there are different, in 
that the whole glenoid cavity is carried by the scapula and the 
single coracoidal element, which extends backward for some 
distance behind it. 
The humerus is distinguished trom that of any Cotylosaur by 
its slenderness, but is probably structurally similar to that of 
Captorhinus. 
The carpus of Broomia is unique, no other form being known 
in which the centralia completely separate the proximal and 
distal rows of carpals. 
The ilium, which alone of the pelvic bones is known in Broomia, 
differs from that of all Cotylosaurs in its slenderness and its 
sloping anterior border. 
The femur is so badly exposed that it is difficult to compare it 
with that of Cotylosaurs, from which, however, it differs in its 
extreme slenderness. The tarsus differs from that of any known 
Cotylosaur in the presence of two centralia. 
These resemblances, particularly those in the vertebral column, 
seem to show that Broomia has descended from some Cotylosaur; , 
the differences, lying chiefly in the build and limb-skeleton, are in 
general advances of an adaptive nature, but the tarsus is the 
most primitive known amongst reptiles, and the carpus cannot at. 
present be explained. 
Comparison with the Therapsid stock. 
Varanosaurus and its immediate allies amon gst the Poliosauridz 
are the most primitive known members of the Therapsid line, 
and as they are comparatively small and lightly built reptiles, 
offer an exceptionally favourable field for comparison with 
Broomia. 
