550 
PROFESSOR OWEN ON SOME REMAINS OF THE 
Uromastix, from Zanzibar, recently described and figured as U, princeps by my friend 
and colleague A. W. E. O’Shaughnessy, Esq., in the £ Proceedings of the Zoological 
Society of London,’ for June 1, 1880 (p. 445, plate 43). The striking character and 
proportions of the caudal weapons of this Lizard may, perhaps, weigh for admission of 
a copy of the above-cited figure, amongst the illustrations of the present paper 
(Plate 66, fig. 1). In this recent instance, however, the horns, or horny spines, are 
confined to the tail. 
As in Megalcinia they have an annular arrangement and are best developed on the 
dorsal and dorso-lateral parts of each ring. Those (ib., figs. 1-3, b, b) corresponding 
with the dorso-lateral horns in Megalcinia are the largest; the laterals, or medi- 
laterals (ib., c, c ) are relatively smaller : the rest of the lateral and underpart of each 
ring is covered by oblong narrow, flat scales in two transverse series (ib., figs. 2, 3) ; 
the anterior (ib., d, d) short, the posterior series (ib., e, e) long,—an arrangement which 
seems to multiply the number of the cutaneous segments. The spines of second 
degree as to size which spring from the dorsal surface of the tail (ib., fig. 1, a, a) 
are six in number on each ring, arranged in the same transverse line : they are shorter 
than the dorso-lateral series, and slightly diminish toward the mid-line. 
All the spines are rather more compressed, more triangular, more sharply pointed, 
than in Megalania: the series a and b, especially the latter, are relatively larger and 
longer ; but it must be remembered that in the case of the great extinct Lizard we 
have only the osseous cores of these weapons, and that their sheath of true horny 
material may have greatly added to the efficiency of the strange and grotesque 
armature. 
In Uromastix, moreover, as was noted in Part II. (tom. cit., p. 1047) in reference 
to the cranial horns of Moloch, histological development has not advanced in the 
diminutive Lizards beyond the fibro-cartilaginous stage of the productions of the 
corium supporting the corneous sheaths. 
Pursuing this track of comparison it was wfith interest I found in the small 
existing Australian species that, although the caudal horns or spines are relatively 
somewhat smaller in Moloch horridus than in Uromastix princeps, they more closely 
repeated in number and arrangement the conditions of the caudal armature above 
described in Megalania prisca. 
The annular disposition is, in the main, maintained. Taking one of the cutaneous 
rings near the base of the tail the following horns are present (Plate 66, figs. 4, 5, and 6). 
The dorsals (a) are in a single pair, as in Megalania, with an interspace equal to 
their own basal breadth. External to these is a dorso-lateral pair (ib., b, b) divided 
from the dorsals by a space rather wider than their own basal diameter. Next come 
a “lateral pair” (ib., fig. 5, c) projecting from the middle of the side-surface of each 
annular series, but placed, in some of them, rather farther back than the dorso-laterals. 
Then come the spines of a ventro-lateral pair (ib., d) nearly on the same vertical line 
with the laterals ; but, as in Megalania, of markedly smaller size and projecting from 
