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 plesiosaur 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 vertebræ 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
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posterior parts broadly separated (text-figure 2), though this part is unusually wide and short. It has, on the other hand, scapulæ 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 distinguishing 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 vertebræ, a scapula, and a nearly complete fore limb.
