0. C. Marsh — Notes on Mesozoic Vertebrate Fossils. 173 



The tibia is shorter than the femur, and has a prominent 

 cnemial crest. The distal end is much flattened, and the 

 astragalus is closely adapted to it. The fibula is very straight, 

 with its lower end flattened and closely applied to the front of 

 the tibia. The calcaneum is large, with its concave upper sur- 

 face closely fitted to the end of the fibula. Of the second row 

 of tarsals, only a single one appears to be ossified, and that is 

 very small and thin, and placed between the calcaneum and 

 the fourth metatarsal, nearly or quite out of sight. 



The hind foot, or pes, had but three digits, the second, third, 

 and fourth, all well developed and massive. The terminal 

 phalanges were covered with broad hoofs. The first and fifth 

 digits were entirely wanting. 



A comparison of the limbs and feet of Claosaurits, as here 

 described and figured, with those of three allied forms from 

 the Jurassic, Stegosaurus, Laosaurus, and Ca?7vptosaurus, as 

 shown on Plates IV and Y, is especially instructive. These 

 three genera have already been quite fully described and 

 figured by the writer, but new points of interest have been 

 made out by the recent investigation of more perfect material. 

 The present figures will show more accurately some of the 

 mutual relations of these early herbivorous Dinosaurs to each 

 other, as well as to their successors in Cretaceous time. The 

 gradual changes that can be traced from one to the other will 

 be discussed in a later communication. 



Palceoscincus, Leidy, 1856. 



A new reptilian genus and species, Palceoscincus costatus, 

 was proposed by Dr. Leidy in 1856 for a single tooth found by 

 Dr. Hayden in the Judith Basin. This tooth was more fully 

 described and figured by Leidy in 1859.* The specimen 

 showed well-marked characters, and many similar teeth have 

 since been found, both in the Judith Basin and in various 

 other localities of the Laramie. 



A smaller species, apparently of the same genus, is not 

 uncommon in the Ceratops beds of "Wyoming, and a character- 

 istic tooth is shown on Plate III, figure 3. This may be taken 

 as the type specimen, and the species it. represents may be 

 called Palozoscineus latus. The crown of the tooth in this 

 species is broader and the apex more pointed than in the first 

 species described, and this is clearly shown in comparing the 

 present figures on Plate III with those given by Leidy. 



* Proc. Acad. Nat. Sci. Philadelphia, p. 72, 1856; and Trans. Amer. Phil. Soc, 

 p. 146, pi. ix, figs. 49-52, 1859. 



