200 Systematic Paleontology 



A second metatarsal (No. 5660, U. S. National Museum) has the 



following dimensions : 



Length 77 mm. 



Width proximal end 54 mm. 



Width distal end 38 mm. 



The ungual phalanx, cotype JSTo. 2267, U. S. National Museum, here 

 figured (pi. xviii, fig. 2), has the following measurements : 



Length 58.7 mm. 



Width proximal end 35.5 mm. 



Thickness 18.5 mm. 



Occurrence. — ^Arundel Formation. Near Muirkirk, Prince George's 

 County. 



Collections. — TJ. S. National Museum, Goucher College. 



Pleuroccelus altus Marsh ' 



Plate XYIII, Fig. 3 ; Plate XIX, Figs. 1-4 



Pleuroccelus altus Marsh, 1888, Amer. Jour. Sci., ser. iii, vol. xxxv, p. 92. 

 Pleuroccelus altus Hay, 1902, Bull. U. S. Geol. Survey, No. 179, p. 483. 



Description. — The type specimen is a tibia and the proximal and distal 

 ends of a fibula (No. 4971, U. S. National Museum). Marsh's original 

 description is as follows : " A larger species, apparently of the above 

 genus, is represented by various remains from the same localities as the 

 specimens just described. A tibia and other limb bones show the animal 

 to have had elongated posterior extremities, at least a third longer pro- 

 portionately than in Morosaurus, which these remains, in some respects, 

 clearly resemble. 



" The tibia has the proximal end compressed transversely, with its 

 outline subrhomboidal. The shaft is solid throughout, with the excep- 

 tion of a very small cavity near the middle, and here it is subovate in 

 transverse section. The distal end is much flattened antero-posteriorly, 

 and the notch in the articular face, characteristic of the Sauropoda, is 

 well marked. This tibia is twenty-five inches (635 mm.) in length, with 

 its proximal end seven inches (177 mm.) in fore and aft diameter, and 

 the distal end six inches (152 rmn.) in transverse diameter. Both ex- 



