122 SAMUEL WENDELL WILLISTON— LULL. IM " MW "vK?n; 



does O. P. Hay in his catalogue of fossil Vertebrata (1902). This paper of 1893 gives further 

 morphologic description of the pelvis and hind limb of Pteranodon (Ornithostoma) ingens. 



But three more papers on this interesting group appear from his pen: on the mandible 

 of Ornithostoma (1895) , 21 on the skull (1896) , 22 and a restoration in 1S97. 26 In his report on 

 the Geological Survey of Kansas, 1898, there is a view (frontispiece) of the reptiles of the Kansas 

 Cretaceous ocean, previously published in Popular Science Monthly, in which a number of 

 pteranodons are seen, one clinging to the cliff, the others in the air, and none of them display the 

 crest in its full development as held by Marsh and now abundantly proved to be correct. 



In 1902 5e 63 and 1903, 68 Williston described in detail a remarkable specimen of Nyctodactylus 

 which had recently been discovered in the Kansas Chalk and which was so complete that many 

 details of anatomy of the group were learned from it. As usual, not only does he give a very 

 detailed description of the morphology of the animal, but his picture of its small body, not 

 larger than one's fist, compared with the 8 feet of wing expanse, the peculiar articulation of the 

 hind limbs, giving it a most laborious gait when on the ground, and the conjectures as to its 

 young, which could not have been viviparously born — all have a striking interest to one who 

 would visualize as living beings the creatures of the past. His arguments, moreover, are so 

 complete that one feels instinctively that his conclusions are well founded 



mosasauks. 



The paper on the Kansas mosasaurs in 1S91 8 gives the first morphologic description of a 

 complete skeleton of a member of this interesting group, although, as Williston says, Baur had 

 aire idy studied and figured another genus, the description of which had not been published. 

 In his introduction, Williston discusses the nomenclature of the mosasaurs, with its very much 

 confused synonymy, which he later was privileged partially to unravel. In his morphologic 

 description he shows his powers of visualizing as a living form the creature under his observation, 

 for, as he says (p. 345) : 



It is doubtful whether there was ever another vertebrate animal so admirably adapted for rapid and varied move- 

 ments through the water. Though the smallest of the mosasaurs, it [Clidastes velox] was by far the most graceful in its 

 proportions, the most delicate and exquisitely constructed in its details. 



Marsh had denied the presence of sclerotic plates. Williston, however, says: 



It is certain that none of the Kansas forms of this order were covered with bony scutes, as described by Marsh, the 

 bones so described being, undoubtedly, sclerotic plates. 



This observation was subsequently verified by the finding of impressions of the mosasaurian 

 skin. 



In 1892, 10 Williston, aided by his pupd, E. C. Case, wrote still more extensively of the 

 mosasaurs of Kansas. This work, Part I, includes the genus Clidastes, and opens with the usual 

 specific list and the authors' conception of the synonymy. Then follows a morphologic descrip- 

 tion of C. velox and a discussion of the synonymy. The new species, C. westii, is also described 

 in comparison with its nearest allies. 



The next year 12 Williston published his first restoration of a mosasaur, that of C. velox 

 {vide supra), which, with certain modifications, served as a basis for his restoration of 1897 that 

 has since become standard. No further mosasaur papers appear until 1897, when a new genus, 

 Brachysaurus, is described, 29 the extremities of Tylosaurus, discussed, 30 and the principal genera, 

 Clidastes, Platecarpus, and Tylosaurus, restored as full length, rather diagrammatic skeletons. 

 These figures are also now accepted as standard and have been republished a number of times. 



"The Range and Distribution of the Mosasaurs," 1897, 32 is an extremely important paper in 

 which Williston discusses not alone the synonymy, but also the geographic and geologic range 

 of the entire group, together with some important generalizations concerning their distribution 

 and relationships. 



Then follows Williston's monumental work on the Upper Cretaceous paleontology of 

 Kansas, 1898, 30 in which no fewer than 13S pages and 62 plates refer to the group under discus- 

 sion. This work virtually completes Williston's investigations of the mosasaurs, for but three 



