1869.] HUXLEY—HYPSILOPHODON. 9 
to my mind. On the other hand, my present knowledge of the 
strange characters of the pelvis in the Dinosaurian reptiles led me. 
to suspect that those bones might prove to be the pubis and ischium 
wm situ, and in their natural connexion with the right ilium, the 
posterior part of which bone (numbered 62 in the plate cited) was 
conspicuously visible. Careful search revealed the anterior end of 
the bone overlying the arch of the posterior vertebree of the dorsal 
series. 
With the permission of the Keeper of the fossil collection, there- 
fore, the specimen was subjected to a further careful removal of the 
matrix in the requisite directions. The result has been the com- 
plete verification of my conjecture, and the specimen now affords 
a view of the ventral elements of the pelvis in their natural re- 
lations (Pl. IT.). 
The middle part of the right ilium is covered, and, seemingly, a 
little crushed in, by the left foot. But its broad postacetabular por- 
tion (6), and its relatively narrow and pointed preeacetabular part (a) 
are completely exposed. I suspect that the ilium is broken in the 
middle, and, as a consequence, that the distance from the postericr 
to the anterior ends of the visible parts of the bone (6-6 inch) is 
somewhat greater than it should be. Hence the acetabulum pro- 
bably appears to be longer than it naturally is. The postacetabular 
process (c), which should articulate with the ischium, is swollen and 
thick, but thins off, above and behind, into a thin vertical plate, the 
posterior curved margin of which is broad and turned in, like a narrow 
shelf. The preeacetabular prolongation is slender, and its broken 
narrow end (a) rests on the arch of the seventeenth vertebra. 
The anterior boundary of the acetabulum is formed by a broad, some- 
what flattened, facet of bone (¢), which looks backwards and a little 
outwards. The osseous mass, of which this forms the posterior aspect, 
rapidly narrows forwards, and is prolonged above into a slender ridge, 
or process, with a free rounded end (a). In front, it has a sinuated 
free edge; anteriorly and below, it is continued into a slender rod-like 
pubis (Pb), between six and sevenincheslong, which passes downwards 
and backwards parallel with the ischium. On the outer surface, in 
front of the lower part of the articular surface, lies an oval foramen (e). 
The posterior edge of the bone is concave and free. Posteriorly and 
below, it ends in a broad thin prolongation, which passes backwards, 
internal to the ischium. The part of the bone which bears the facet 
answers very well to the preacetabular process of the ilium of Me- 
galosaurus and of Thecodontosaurus. The perforation is indeed some- 
what like that which is so generally found in the pubis of Lizards ; 
but, on a future occasion, I hope to be able to show its analogue in 
the ilium of an undoubted Dinosaurian. If this part of the aceta- 
bular wall answers, as I believe it does, to the descending preeaceta- 
bular process of the ilium, all trace of the suture between it and the 
pubis has disappeared. 
The right ischium (Js) lies in undisturbed relation with the pubis. 
Its acetabular end has a free superior concave edge which bounds 
the acetabulum below, a broad thin anterior process which over- 
