Maryland GtEOLogical Survey 187 



Occurrence. — Arundel Formation. Washington, District of 

 Columbia. 



Collection.— \J. S. ISTational Museum. 



Family COELURIDAE 



Genus COELURUS Marsh 

 CcELURUS GRACILIS Marsli 



Plate XV, Fig. 1 ■ 



Calurus gracilis Marsh, 1888, Amer. Jour. Sci., ser. iii, vol. xxxv, p. 94. 

 Coelurus gracilis Zittel, 1890, Handbuch der Palaeontologie, Abth. i, Bd. iii, 



p. 732. 

 Goelurus gracilis Hay, 1902, Bull. U. S. Geol. Survey, No. 179, p. 493. 



Description. — The type specimen is No. 4973, U. S. JSTational Museum, 

 an ungual phalanx from near Muirkirk, Maryland. Additional material 

 consists of ISTos. 3336, 3338, and 8176, Goucher College, and embraces 

 three teeth, the first two coming from the same locality as the type. 



The original description is as follows : " The smallest Dinosaur found 

 in these deposits is a very diminutive carnivore, apparently belonging 

 to the genus Coelurus. It was not more than one-half the size of the 

 western species, and its proportions were extremely slender. The bones 

 are very light and hollow, the metapodials being much elongated and 

 their walls extremely thin. An ungual phalanx of the manus measures 

 about 25mm. in length; and 14mm. in vertical diameter at the base. 

 This ajiimal could not have been more than 5 or 6 feet in length.^' 



The ungual phalanx is from the manus, and from the great develop- 

 ment of the base below the articulation must have constituted a powerful 

 grasping organ when one considers the size of the entire animal. 



The teeth resemble very closely that of Goelurus fragilis figured by 

 Marsh,'' but differ in the almost total reduction of the crenulation of 

 the anterior convex border, which is perfectly smooth in one of the 

 three specimens, has serrations of almost microscopical fineness for a 

 short distance from the tip in the second, while, in the third specimen, 



^ Marsli, leth Ann. Rept. U. S. Geol. Surv., pt. i, 1896, pi. vii, fig. 1. 



