, VERTEBRATA 



Class REPTILIA 



Order DINOSAURIA 



Suborder THEROPODA 



Family MEGALOSAURIDAE 



Genus ALLOSAURUS Marsh 



xVllosaurus medius Marsh 



Plate XIV, Figs. 1-3 



Allosaurus medius Marsh, 1888, Amer. Jour. Sci., ser. iii, vol. xxxv, p. 93. 

 Allosaurus Bibbins, 1895, Johns Hopkins Univ. Circulars, vol. xv, fig. G. 

 Antrodemus medius Hay, 1902, Bull. U. S. Geol. Survey, No. 179, p. 489. 

 Allosaurus medius Hay, 1908, Proc. U. S. Natl. Museum, vol. xxxv, p. 353. 



Description. — The type (No. 4972, U. S. Kational Museum) consists 

 of a single tooth, the other material mentioned by Marsh in his original 

 description being removed to the genus Dryosaurus (vide infra, p. 204). 

 Marsh's description of the type is as follows : " The teeth are remark- 

 ably flat and trenchant, with the edges finely serrated, and the surface 

 very smooth. . . . One tooth has the crown 30 mm. in height; its antero- 

 posterior diameter at base 15 mm.; and its transverse diameter 7 mm." 



There are several larger, better preserved teeth among the material, 

 one of which (ISTo. 5685, Goucher College) shows decided wear. The 

 most perfect is one in the possession of the Hon. Charles E. Coffm,^ 

 Muirkirk, Maryland (pi. ziv, figs. 1, 2). It is about 3 inches (76 mm.) in 

 length and 1-| inches (28.7 mm.) in the antero-posterior diameter. The 

 crenulations of the margin cease about midway toward the root on the 

 anterior convex border, but extend the length of the crown on the posterior 

 edge. There is a slight variation in the size of the crenulations, as they 

 are somewhat coarser in the larger teeth. 



' Or No. 3121, Goucher College. 



