APRACTOCLEIDUS TERETIPES. 623 



except for the thickening at the symphysis and the two thick bars forming the 

 lateral and posterior margins. These meet in the massive head which carries the 

 acetabular surface. The lateral margin is thin and straight to within cm. of the 

 anterior angle, when it thickens and passes sharply outward into the prominent 

 beak-shaped antero-external angle. The anterior margin of this angle is hollowed 

 and rouo-h for about 7 cm. From this point to the prominent process, which occurs 

 about the middle of the anterior margin, the bone is thin and presents a finished 

 edge ; but from this process inward the margin has again been tipped with cartilage, 

 which was, no doubt, continuous with the median symphysis and the cartilage of 

 the opposite pubis. Approaching the symphysis, the anterior border comes in at an 

 angle slightly greater than a right angle to within 5 cm. of the centre, then turns 

 sharply back and strikes the mid-ventral line at an angle of 45 degrees. This portion 

 of the pubis is strikingly unlike that of Cryptocleidus, where the anterior and inner 

 margins form practically one continuous curve from external angle to symphysis. 

 The symphysial surface is straight, and the two pubic bones must have been 

 practically in contact for a distance of 17 cm. There is no divergence of the bones 

 posteriorly except for a slight reflexion of the posterior extremities, each of which 

 shows a small lip, rough like the rest of the symphysis, serving for the attachment 

 of the cartilage which bridged the gap to the ischiurh and made the division 

 between the foramina obturatoria. The posterior margin of the pubis is concave, 

 and the edge is sharply rounded, only becoming full as it approaches the head. The 

 head carries the acetabular surface, which forms half of an elongated oval and looks 

 outwards and backwards, making an angle of 135 degrees with the articular surface 

 for the ischium. The acetabular surface is smooth and slightly concave. From the 

 surface of union with the ischium, it is evident that at least a partial fusion of the 

 pubis and ischium has taken place ; the bones have not separated along a symphysis, 

 but have broken, leaving, in one place, a piece of the pubis still fused to the ischium 

 along an interlocking suture line. 



The ischium consists of a massive head carrying the three articular surfaces, a 

 rather weak neck oval in section, and the broad expansion in which it approaches 

 the mid-ventral line. The acetabular surface, looking out and slightly up, occupies 

 most of the head, and the surface for the ilium is much smaller and faces out, back, 

 and up. The anterior margin of the bone forms the posterior border of the obturator 

 foramen, and like the posterior border of the pubis it is concave and its edge is thin 

 and sharply rounded. The symphysial border is deepest in the anterior third. It 

 is straight or slightly convex for about 16 cm., after which it curves rapidly outwards 

 and meets the posterior border in a right angle. The surface, all its length, is rough 

 and hollow, indicating a cartilaginous continuation with the opposite ischium. The 

 posterior border is concave and smooth except for a rough ridge near the posterior 

 angle. The inner (visceral) side of the head of the ischium is roughened into 

 very prominent tuberosities in the angle formed by the edges of the acetabular and 



