SKELETON OF PHOEOEHACOS INFLATUS. 73 



regarded as lumbar ; the last of these bears a broad parapophysial process which abuts 

 against the inner border of the ilium. Behind this there seem to be two or three 

 lumbo-sacrals (Mivart) in which no parapophyses are present and, except perhaps on 

 the hinclermost, no diapophyses, unless these are directed dorsad. In this region the 

 pelvis is very narrow, so that the lateral acetabular or anterior renal fossse are extremely 

 small. 



Behind the lumbo-sacrals are the true sacrals, two in number. Both these possess 

 ventral processes, which, no doubt, are formed by parapophyses -f sacral ribs. In the 

 first the process is stout, much expanded at its outer end, and directed outward, upward, 

 and somewhat forward. In the second this process is very slender and quickly fuses 

 with the middle of the upper process (diapophysis), which in this vertebra is stout and 

 directed outward and forward. The diapophysis of the anterior sacral is slightly 

 in front of, and about 1 cm. above, the parapophysis ; it is directed backward, outward, 

 and upward. The two diapophyses are separated by a nearly circular space, and their 

 expanded outer ends, together with that of the ventral process of the anterior sacral 

 fuse into a common mass of bone, which abuts against and fuses with the inner surface 

 of the ilium immediately behind the acetabulum. 



On the vertebral centra, at the level of the second sacral rib, there is a median 

 hsemal ridge, which is continuous as far as the third of the urosacrals which bear 

 transverse processes. 



Behind the last sacral there is an interval in which no transverse processes are 

 present : then they reappear, the first being very slender and directed backward at a 

 very acute angle with the vertebral column ; at its distal end it fuses with the succeeding 

 process. This also is directed backward, but is much stouter than the last and greatly 

 expanded at its distal end, where it abuts against the inflected portion of the ilium 

 forming the floor of the pocket-like renal fossa. The next transverse process is very 

 broad, and likewise unites externally with the ilium ; it is separated from the processes 

 in front of and behind it by oval foramina. Behind this there are four pairs of similar 

 processes borne by vertebrae with long, narrow centra having a slight haemal ridge. The 

 free end of the last fused centrum is flat or slightly convex. On the dorsal surface the 

 neural spines of the postacetabular " sacrals " form a prominent median ridge, separated 

 from the ilia, anteriorly at least, by a narrow groove ; posteriorly there are several pairs 

 of slit-like interosseous foramina. 



The pelvis, seen from above (Plate XVI. fig. 1), appears very long and narrow, the 

 postacetabular region not being expanded to any great extent. Along the middle 

 line runs a prominent ridge, formed in front by the fused upper edges of the ilia and 

 behind by the united neural spines of the postacetabular vertebra?. Opposite the 

 hinder border of the acetabulum is a transverse ridge which, at its outer ends, rises 

 into a pair of very prominent supra-trochanteric crests ; these, with the anti-trochanters, 

 form prominent lateral projections. On each side of the median ridge in the post- 

 acetabular region there is a narrow groove separating it from the upper edges of the 



M 2 



