75 
In 1900 Lucas called attention to the identity of the types of 
Thespesius occidental is Leidy and Claosaurus annectens 1 Marsh. In 
1915 Gilmore published a short article 2 in which he says, in part: 
“I have recently compared the types. Thespesius occidentals Leidy and Claosaurus 
annectens Marsh, and can testify to the close similarity of the homologous bones. The 
inadequacy of the type material upon which Thespesius is based (two caudal vertebra* 
and a proximal phalanx) is fully recognized, but that these pertain to a Trachodont dinosaur 
there can be no doubt. It is now positively known from the geological mapping done 
in recent years in the locality where the type material was obtained, that the specimen 
came from the Lance formation on Grand river in what is now the state of South 
Dakota. . . While it can not be positively determined that occidentalis and annectens 
are identical it is equally true that they can not be shown to represent distinct species. . . 
I would, therefore, endorse the use of Thespesius occidentalis as proposed by Lucas.” 
A comparison of anterior caudal centra of the type of Thespesius 
saskatchewanensis n. sp., with those of the type of Thespesius occidentalis 
as figured and described by Leidy,® shows no generic distinction. 
As pointed out by Gilmore the type material on which Thespesius 
occidentalis is based is inadequate, but as Thespesius is the only generic 
name ever established on a hadrosaurian dinosaur collected from the 
Lance formation, and as the present specimen shows no generic distinction 
from the type of the genus, it is considered advisable to refer the Saskatch- 
ewan specimen to that genus while awaiting a thorough revision of the 
Hadrosauridae. 
DESCRIPTION OF SPECIES 
Thespesius saskatchewanensis n. sp. 
Type, Cat. No. 8509, Geological Survey, Canada, consists of skull, 
almost complete; sixteen dorsal vertebrae; thirty-seven caudal centra, 
fragmentary chevrons, left scapula and coracoid, left femur and part 
of the right, right tibia with astragalus and calcanium, both ischia and 
some fragmentary ribs. With the exception of the skull all the bones 
were disarticulated. 
Locality and Horizon . Rocky creek, Saskatchewan; Lance formation, 
uppermost Cretaceous. Collected by C. M. Sternberg. 
The caudal centrum, Cat. No. 8509, Geol. Surv., Canada, Plate XVII, 
figures 2 and 3, which has been chosen for comparison with Leidy’s type 
of T. occidentalis , of those present, most nearly resembles the one figured 
by Leidy and judging from the stage of development of the lateral pro- 
cesses and chevron facets, is thought to be the sixth of the caudal series. 
Viewed from the front it is roughly circular in outline with a transverse 
diameter of 110 mm. and a vertical diameter of 105 mm. taken at the 
centre of the face. It is 63 mm. in length. The anterior face is slightly 
convex and the posterior face is concave to the extent of 13 mm. Just 
below the centre, on the anterior face, is a well-marked circular convexity 
40 mm. in diameter. In the vertebrse immediately succeeding the sixth 
caudal the posterior faces are more deeply concave and the anterior faces 
are less convex. 
iUci., New Ser., vol. XII, pp. 80B-810 (1000). 
* Sci., New. Ser., vol. XLI, pp. 668-660 (1916). 
* Trane. Am. Phil. Soc., vol. XI, PI. 10, figs. 1-3 (1860). 
