78 



THE CERATOPSIA. 



the same skeleton, though with a query. It differs little from the same bone in AgatTiaumas, 

 except m its smaller size. It is proportionally longer and more slender in the present genus 



Fig. 82.— A, Inferior view of right ilium (No. 3998? American Museum of Natural History) of Monoclonius crassus Cope; B, superior view of 

 same, a, Anterior extremity; p, posterior; is, ischiac peduncle; pb, pubic peduncle; «s, surface for contact with sacrum. One-eighth 

 natural size. 



and has the deflected external 

 margin posterior to the ischiac 

 peduncle more marked and pro- 

 duced into a somewhat angular 

 prominence. The extreme ante- 

 rior end of the blade is wanting, 

 but otherwise the bone is essen- 

 tially complete. 



Superior and inferior views of 

 this ilium are given here in fig. 82. 



I have been unable to detect 

 any portion of either pubis among 

 the collections from the Judith 

 River beds. There is a left 

 ischium nearly complete, but 

 lacking the extremity of the 

 anterior process with the articular 

 surface for the pubis and the 

 extreme distal end of the shaft. 

 This agrees very well in size and 

 general characters with the other 

 fig. 83.-Extemai view of ischium of Mono- material that has been referred 



clonius crassus Cope, No. 3998, American Uy CoDe to 31 CTdS^US I there- 

 Museum of Natural History, il, Proc- J . . 



fore describe and figure it m this 



connection. In general form the 



ischium in the Ceratopsia is not 

 very unlike a rib, and after a casual glance it might be mistaken 

 for one of those elements. More careful study, however, will at 

 once reveal its identity. Proximally it presents a moderately 

 expanded subcircular articulation for contact with the ischiac 

 peduncle of the ilium. Just below this it sends forward a rather 

 slender process for articulation with the pubis. The extremity 

 of this is wanting in the present specimen. The shaft of the ischium is subcircular in cross 



ess for contact with ilium; p, process 

 for contact with pubis. One-eighth 

 natural size. 



Fig. 84. — External view of right scapula 

 and coracoid of Monoclonius crassus 

 Cope, No. 3998a, American Museum 

 of- Natural History. S, Scapula; 

 C, coracoid; g, glenoid cavity; d, ru- 

 gosity for attachment of deltoid 

 muscle; sc, scapulo-coracoid suture. 

 One-eighth natural size. 



