OSTEOLOGY OF CARNIVOROUS- DINOSAURS. 119 



In Tyrannosaurus and Gorgosaurus, however, from the western Upper Creta- 

 ceous, the concavity of this lower surface of the anterior caudals is markedly 

 straighter, and in Dryptosaurus aquilunguis (Cope) from the Upper Cretaceous of 

 New Jersey is found the nearest approach to the straight ventral border of the 

 specimen under consideration. After a careful comparison of the type of C. potens 

 with the description, measurements, and illustration of the anterior caudals of 

 the type of Dryptosaurus aquilunguis* (Cope), 1 and after taking into account the 

 morphological resemblances and the geographical distribution of these specimens, 

 • I believe that, tentatively, it may be best referred to the genus Dryptosaurus. 

 Thus this species becomes Dryptosaurus f potens (Lull) until such time as the dis- 

 covery of adequate materials will permit. the determination 6i its true affinities. 



The median portion of a very large ungual (No. 8505 U.S.N.M.) collected 

 by Arthur Bibbins from the Arundel formation near Contee, Maryland, is, on 

 account of its great size, provisionally referred to the present species. This bone 

 lacks both its proximal and distal ends, but its slightly curved contours with lateral 

 longitudinal grooves indicate the terminal phalanx of digit I of the fore foot. A 

 large medullary cavity is to be seen on the broken proximal end. In size it 

 considerably exceeds any unguals in the collection. 



DRYPTOSAURUS? MEDIUS (Marsh), 1888. 



Plate 34, figs. 1-3. 



Allosaurus rnedius Marsh, 0. C, Amer. Journ. Sci., ser. 3, vol. 35, 1888, p. 93. — Hay, 0. P., Proc. 

 U. S. Nat. Mus., 1908, vol. 35, p. 353.— Merrill, G.P., Bull. U. S. Nat. Mus., 53, pt. 2, p. 63, 

 1907.— Schuchert, Charles, Bull. Geol. Soc. Amer., vol. 20, p. 586, 1910.— Lull, R. S.Mary- 

 land Geol. Surv., Lower Cretaceous, 1911, pp. 183-186, pi. 14, figs. 1-3. 



Antrodemus rnedius Hay, O. P., Bull. No. 179, U. S. Geol. Surv., 1902, p. 489. 



Type specimen. — No. 4972, U.S.N.M. Consists of a single broken tooth. Col- 

 lected by J. B. Hatcher in 1887. 



Type locality. — Near Muirkirk, Prince Georges County, Maryland. 

 Horizon. — Arundel formation, Lower Cretaceous. 



The original description by Marsh is as follows : 



Besides the herbivorous Dinosaurs described above, remains of two carnivorous forms were secured 

 from the same horizon The larger of these, which may be provisionally referred to the genus Allosaurus, 

 is represented by various specimens, the most characteristic of which are teeth and bones of the limbs 

 and feet. The teeth are remarkably flat and trenchant, with the edges finely serrated and the surfaces 

 very smooth. The limb bones and even the phalanges are unusually hollow, and the latter have the 

 articulation finely finished. The principal dimensions of some of the parts preserved are as follows: 

 One tooth has the crown 30 mm. in heighth; its antero-posterior diameter at base 75 mm.; and its trans- 

 verse diameter 7 mm. [See fig. 2, pi. 34.]. 



The astragalus is 55 mm. in width, and 50 mm. in fore and aft diameter. A first phalanx of the kind 

 foot is 90 mm. in length. These specimens would indicate an animal 10 or 12 feet in length. 



In 1911 Lull reached the conclusion that the tooth alone constituted the 

 type of this species, the other material mentioned by Marsh being removed to the 

 genus Dryosaurus. I have examined the cotypes thus referred and concur in 

 the conclusion reached by Lull that these bones do not pertain to a Megalosauroid 

 dinosaur. 



i Trans. Amer. Philos. Soc, 1869, pp. 100-118, fig. 30. 



