206 Systematic Paleontology 



distal facet of the bone is saddle-shaped with regular curves and no 

 trace of a sharp median groove. 



The proximal phalanx of digit iv is represented by two bones, one 

 somewhat smaller than the other. The larger of these (JSTo. 5453, U. S. 

 National Museum) (pi. xx, figs. 1, 2) is part of the cotype of Allosaurus 

 medius. The proximal end is concave and there are two very prominent 

 ridges on the palmar aspect of the proximal one-third. Distally it is char- 

 acterized by a rather pronounced groove in the articular face and the great 

 depth of the external depression. The bone is very hollow, resembling 

 in this respect the metatarsals. 



DIMENSIONS 



Length 88.0 mm. 



Width of proximal end 34.0 mm. 



Depth of proximal end 38.5 mm. 



Width of distal end 31.5 mm. 



Depth of distal end 28.5 mm. 



Width of shaft 20.0 mm. 



The distal phalanges (pi. xx, fig. 3) are typical with proximal ridge and 

 distal groove, effectually limiting motion other than in the vertical plane. 



The ungual (pi. xx, fig. 4), which is here referred to this species, is com- 

 pressed, triangular in section, the upper face bearing a rather sharp ridge 

 which separates it from those of Laosaurus consors, those of Dryosaurus 

 alius being unknown. It has a gentle curve with the characteristic 

 slightly hollowed under surface of Laosaurus and ihe smaller Campto- 

 saurus species. 



DIMENSIONS 



Length 55.5 mm. 



Height 26.0 mm. 



Width 17.0 mm. 



Judging from the comparative size of Dryosaurus grandis and D. alius 

 one would perhaps be justified in assuming the present individual to 

 have attained the length of about 13 feet, using Professor Marsh's esti- 

 mate of 10 feet for the latter species. 



Occurrence. — Arundel Foemation. Near Muirkirk, Prince George's 

 County. 



Colleciions. — U. S. National Museum, Goucher College. 



