478 
SIR R. OWEN ON THE FOSSIL REMAINS OF TWO SPECIES 
Reptilia, both, extinct and existing, a like coalescence of the vertebral elements was 
found in the small existing Australian lizard (Moloch). 
As this osteological character is the rule in the “warm-blooded” Vertebrates, the 
neural arch retaining, for the most part, its earlier stage of development in the cold¬ 
blooded air-breathers, I was, in some measure, prepared by structures above described 
to recognise a corresponding advance of osteogeny in the piers of the pelvic arch of 
Meiolania. 
In Anthropotomy the pelvic elements, recognised as becoming ossified from three 
chief centres, received the names of “ilium,” “ischium,” and “pubis”; but, coalescing 
into a single bone in the adult, this was described as the “nameless bone' - — os inno- 
minatum. Such coalescence is rare in the class Reptilia, and it adds to the singular 
characters of the Megalanian Family of the Antipodes. I subjoin three figures of this 
“innominate” fossil from Lord Howe’s Island, and on the grounds of locality and 
contiguity refer it to the genus Meiolania. The coalesced pelvic elements are denoted 
in Plate 32, figs. 1, 2, and 3, by the numerals indicative of them in the descriptions of 
the modifications of that part of the reptilian skeleton in my ‘ Anatomy of Verte¬ 
brates.’* Reference to those figures will show the contrast betwmen the expanded 
( Mammalian ) character of the bone, 62, in Crocodiles, and the almost columnar form 
in the Lacertian pelvis. This latter form is attained or retained in Meiolania. The 
ilium, 62, is a triedral column, moderately expanded at the proximal end to join by a 
rough syndesmosis with a short sacrum; and, at the distal end, to contribute its 
share to the acetabulum, a. One angle of the shaft or body of the bone looks out¬ 
ward, one plane inward. The anchylosis of the osseous elements, which has dominated 
to an unusual extent in the skull of the Megalanian family, prevails in the pelvis. 
There is no trace of a suture which would indicate the share taken by the ilium in the 
formation of the acetabular cavity. 
The upper or “ proximal” end of the triedral ilium expands in a moderate degree to 
unite by a rough surface (fig. 2, s ) with a sacrum. The opposite, outer, surface of this 
expansion (fig. 1) is also roughened, but in a minor degree, for attachment of a 
“ glutseus ” muscle. Acetabular sutures indicative of the shares respectively taken by 
the ischium, 63, and pubis, 64, are also obliterated by the firm anchylosis of the pelvic 
bones of this powerful extinct Saurian. The contour of the acetabulum deviates 
slightly from the circular toward the triangular form : the ischial and pubic angles 
are rounded off (fig. 1, a). The diameter of the acetabular outlet gives two inches : 
the depth of the cavity is rather less than one inch. These dimensions indicate the 
femur of Meiolania to have equalled that of the largest known Crocodilian in size. 
Of the pubic element, 64, little more than two inches are preserved : the bone 
contracts to a triedral form as it recedes from the articular cavity for the thigh-bone. 
A smaller proportion of the ischium, 63, is preserved, and it indicates an assumption 
of a more lamellate figure as it recedes from the acetabulum. The length of the 
* Vol. 1, 1866, p. 188, fig. 119, Crocodilus; p. 191, fig. 121, Monitor. 
