300 LEADING AMERICAN MEN OF SCIENCE 



species, and enabled him to publish a restoration of the principal 

 type, but the projected volume on this peculiar group was never 

 completed. With a group of horned animals nearly equalling the 

 elephant in size the gigantic mammals from a restricted area in 

 the Eocene he was more successful, and the series of papers 

 descriptive of these forms culminated in 1886 in his second mono- 

 graph, that on the Dinocerata. These huge beasts existed in great 

 numbers in central Wyoming, where many of them were entombed 

 and preserved, and more than two hundred individuals now 

 have representation in the Yale collection. 



Rivaling these investigations in the Tertiary deposits were 

 those made in the Mesozoic of the West, which furnished material 

 for numerous contributions to science from 1871 on. Previous to 

 this he had described a few remains of birds from the Cretaceous 

 of New Jersey and from various Tertiary deposits in this country, 

 but all pertained to comparatively small species and apparently 

 belonged to families still existing. In a letter to Professor Dana, 

 under date of November 29, 1871, Marsh announced the dis- 

 covery of his Kansas Cretaceous birds, although the fact of their 

 possessing teeth was not learned until 1873. This announcement 

 was soon followed by a preliminary description of Hesperornis 

 regalis. Subsequent discoveries in the same region in Kansas, 

 accompanied by the investigation of accumulating material and 

 by the publication of results, finally led to the appearance, in 1880, 

 of Marsh's first great monograph: Odontornithes, or The Extinct 

 Toothed Birds of North America, a work which included complete 

 restorations of two distinct types, Hesperornis and Ichthyornis, 

 the one possessing teeth in grooves and the other teeth in sockets. 

 It was published as one of the volumes of the U. S. Geological 

 Exploration of the 4oth Parallel, of which Clarence King was the 

 chief. This work subsequently called forth the following letter 

 from Darwin: 



"MY DEAR PROFESSOR MARSH: I received some time ago your 

 very kind note of July 28th, and yesterday the magnificent vol- 

 ume. I have looked with renewed admiration at the plates, and 

 will soon read the text. Your work on these old birds, and on 



