272 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1918. 



the ribs attached to their respective vertebrae, and the great thigh 

 bones remaining in their sockets, the legs being retained in a walking- 

 position as shown in the reproduction of the mounted skeleton. 



Unfortunately the wearing away of the inclosing sandstone in 

 which the skeleton was embedded had exposed some of the bones and 

 portions of them had been damaged prior to its discovery. This 

 refers especially to the front half of the skull, which had entirely 

 weathered away. This has been restored from another more perfect 

 skull, as have other minor parts of the skeleton which were missing. 

 The skeleton is 26 feet 4 inches long; 11 feet 6 inches high from the 

 base to the top of the head, and 8 feet 2 inches to the top of the 

 hips. The skull is 3 feet 5 inches long; the thigh bone 3 feet 4 inches, 

 while the track of this animal would have been about 21 inches in 

 length and breadth. This is. not the largest individual of its kind, 

 there being several known skeletons that reach a length of 30 and 

 more feet. 



One of the most remarkable features of this great brute is the set 

 of teeth with which the jaws were so well provided. In one respect 

 these reptiles are much better off than the human being, in that as a 

 tooth is worn out or lost it is replaced at once by another pushing up 

 from beneath. Each jawbone has from 45 to 60 rows, and from 10 

 to 14 teeth in each vertical row, one above the other, the entire series 

 moving slowly upward, and new germ teeth continually forming at 

 the base to supply those worn away at the top. Thus it will be seen 

 by a simple computation that there were over 2,000 separate teeth 

 in the mouth of one individual. 



The broad duck-like beak in life was probably covered with a 

 horny sheath, as in birds and turtles of to-day, and admirably suited 

 to the pulling up of rushes and other water plants, for this great 

 creature was a herbivorous or plant-eating animal. That Tracho- 

 don was water-living is indicated by the webbed fingers of the fore 

 feet and the long, deep latterly compressed tail, a most efficient 

 swimming organ and equally useful as a counterbalance to the 

 weight of the body when striding around on the hind legs on the 

 land. Specimens have been found showing impressions of the skin 

 covering, from which it has been learned that the animal Avas cov- 

 ered with a thin epidermis made up of tubercles of two sizes, the 

 larger ones, as has been pointed out by Prof. Henry F. Osborn, pre- 

 dominating on surfaces exposed to the sun. 



In the lower figure of plate 1 is a model restoration by the writer 

 based so far as the proportions go on the mounted skeleton shown 

 in the upper figure. The skin pattern is based with modifications 

 on the published description of the wonderfully preserved mummi- 

 fied carcass of Trachodon in the American Museum of Natural His- 



