430 MR. J. W. HULKE ON THE SKELETAL [NoV. 20, 



a cartilaginous band, as in extant Crocodilians. The posterior border 

 oi the ilium is short, and it is slightly encroached upon by the sutural 

 pit for the attachment of the second sacral rib. The upper border 

 widens anteriorly, and it ends in a short spur {pa) directed forwards. 

 This overhangs the anterior border, which is long and straight. The 

 median surface is indented, above, by two rough pits (s) for the attach- 

 ment of the sacral ribs. The upper limits of these are slightly overhung 

 by the inner lip of the upper border. Below these sutural impressions 

 is a larger trihedral, relatively smooth area, corresponding to the 

 acetabular hollow in the outer surface. No portion of the median 

 surface lies above the level of the sacral articulations, a feature which 

 sharply distinguishes the ilium of Metriorhynchus from that of 

 Steneosaurus, and also from those of Eusuchia. 



Ischium. — This is a large, fiat, triangular bone. The median 

 border {m), which met that of the other side as a ventral 

 symphysis, and the posterior border are almost straight. The 

 anterior border (a), shorter, has a concave outline. The anterior 

 median angle is acute, the posterior is rounded off. The outer angle, 

 bearing the coxal articulation, is the stoutest part. It is subdivided 

 by a notch into (1) a wide oval posterior portion, and (2) a narrow 

 anterior salient process, corresponding to the two divisions of the 

 iliac component of the joint. 



Os Pubis (Plate XX. fig. 6). — This bone is long, flat, spatulate or 

 paddle-shaped, being very similar in form to that in extant Cro- 

 codiles. 



The acetabulum in these Mesosuchia was composed, as in Eusuchia, 

 by the ilium and ischium alone, to the exclusion of the os pubis, 

 which presumably was connected only with the ischiatic process and 

 the cartilage intercalated between this and the ilium. 



The morphology of these three components of the pelvic girdle 

 has occasioned almost as much discussion as that of the component 

 parts of the atlas. 



As an excellent summary of it has lately appeared in Bronn's 

 Klassen, Rept. S. 53 u. f., by C. K. Hoffmann, and as now there 

 is a general agreement that the ilium and the ischium in Crocodilia 

 are respectively simply the equivalents of the bones so named, in 

 higher Vertebrates, it is unnecessary here to review the opinions 

 which different writers have formerly expressed of the essential 

 nature of these two bones. But the morphology of the part here 

 named pubis requires consideration because very recently proof has 

 been offered by Prof. H. G. Seeley that it cannot properly be identified 

 with the OS pubis of higher Vertebrata, and that it must be regarded 

 as "a distinct element of the skeleton, which is connected with the 

 pubic portion of what I (Prof. H. Gr. S.) term ischio-pubic^ bone 

 and is in the position of the pree-piihic bone" (37). Here Prof. H. G. 

 Seeley apparently adopts Fiirbringer's views respecting the dual com- 

 position of the bone, by most writers considered to be the ischium 

 only. He also, in the paper from which the above quotation is taken, 

 cites with approval Hoffmann's (earlier) interpretation of the pubis 

 ^ Italics are mine. — J. W. H. 



