S. W. Williston — Worth American Plesiosaxirs. 229 



excellent specimen in the Yale collection (No. 1644), collected 

 in 1874, by the late Professor B. F. Mudge, with my assistance, 

 on Plum Creek, in western Kansas. It was the first specimen 

 of plesiosanr that I ever saw. The locality of its collection is 

 only a few miles distant from, and in almost precisely the 

 same horizon as, that of the type specimen of the species, 

 which was obtained from Hell Creek by the late Judge West, 

 in 1890. Fortunately, the Yale specimen has, in addition to 

 numerous vertebrae which quite agree with those of the Kansas 

 specimen, parts of the girdles and limbs. I suspect that the 

 specimen represents a somewhat immature animal ; if not, it 

 offers almost generic differences from the E. platyurus. The 

 coracoids are of the true elasmosaurian type, that is, with the 



Figure 3. — Pubes of Elasmosdurus snoivii Williston. Specimen No. 

 636, Yale Museum. 



posterior parts broadly separated (text-figure 2), though this 

 part is unusually wide and short. It has, on the other hand, 

 scapulae of the usual type, not very much widened in the pro- 

 scapular part. The humerus is quite elasmosaurian also, 

 resembling that of E. ischiadicus, though shorter (Plate III, 

 figure 3). The pubis is, however, very distinctive, readily dis- 

 tinguishing the species from E. ischiadicus, in that the anterior 

 and external borders are markedly concave, and the symphysial 

 border is much prolonged (text-figure 3). Another specimen 

 of much larger size, in Yale Museum (No. 1641), has a pubis 

 strikingly like this, though the femur is elongated and the 

 epipodials are. short. 



Elasmosaurus (? ) marshii n. sp. Niobrara Cretaceous of Kansas. 



The specimen upon which this species is based is No. 1645 

 of the Yale Museum, collected in 1889 by Mr. H. T. Martin, 

 in the chalk of Logan county, Kansas. It consists of thirty- 

 two vertebras, a scapula, and a nearly complete fore limb. 



