BY C. W. DE VIS, M.A. 27 
region, but it occupies a larger proportion of the whole breadth. 
This points to a more robust fore-arm and paw and through 
them to some variation or restriction of habit. We are further 
led to observe that the least departure from the proportions of 
the fossil humerus is made by that of M. gouldi among the 
living species compared with it. 
On the palmar or hinder aspect of the bone, the eye notes at 
once the unusually deep depression of the olecranal fossa 
(Pl. 1, of.), its depth being apparently exaggerated by the 
turgescence of the rotulo-condylar region (Pl. 1, r.c.)—the 
large medullary foramen (Pl. 1, mf.) is situated on its 
outer edge, not at its apex as in living genera. The supinator 
ridge (Pl. 1, sx.) is strongly developed and, proximad, 
terminates in an oval tuberosity, 1°75 c.m. in length, for the 
attachment of the supinating muscle, which must have been of 
large volume and, therefore, much used in the motions of 
the fore-limb. Immediately below the tuberosity the ridge is, 
as usual in this group, perforated by a tunnel for the passage of 
the great ulnar artery and nerve. In recent forms the perfora- 
tion is much nearer the end of the ectepicondyle (Pl. 1, e.c.t.) 
This latter region is almost engrossed by an irregular depression 
for the origin of the extensor carpi radialis and differs but little 
in shape from that of Hydrosaurus. On the entepicondylar 
surface (Pl. 1, ent.) the insertion of the coracobrachialis is 
into an elongated prominence placed more proximad than the 
rounder prominence in Monitor and contrasting with the 
depression for the same muscular insertion in Hydrosaurus. 
The radial condyle (PI.. 1, r.c.) is narrower and lower, relative 
to the ulnar, than in either of the existing genera; the ulnar 
(Pl. 1, u.c.) condyle broader, less convex than in Hydrosaurus 
and much lessso than in Monitorand Odatria; its inner limit is 
conspicuously defined by a raised lip continued from the dorsal 
aspect to the olecranal pit, and forming a groove between its 
inner side and the entepicondyle—this lip is not developed 
