236 FOSSIL TURTLES OF NORTH AMERICA. 



mm. wide, 6 mm. thick at the articulation with the neural, and 3 mm. at the sutural border, 

 just beyond the costo-vertebral sulcus. The proximal end is occupied by one of the vertebral 

 scutes. Near the posterior border of the bone the scute overlapt the bone about 20 mm. 

 The sulci are rather narrow. A broad band of fine striations borders the sutures, the striations 

 being at right angles with the latter. The remainder of the surface is markt by delicate ridges 

 and pits appreciable only under a lens. 



The other fragment mentioned belonged to the third or the fifth costal of one side or the 

 other; and it bears a portion of the sulcus between two vertebral scutes. This sulcus extends 

 along the bone a distance of 27 mm. without joining the costo-vertebral sulcus ; so that we 

 may conclude that the hinder vertebral scutes were somewhat wider than the anterior. 



This species is included by Cope in his list of Judith River fossils, but the writer knows 

 of no specimens that confirm the statement. 



Genus ADOCUS Cope. 



Carapace firmly articulated to plastron by sutures between the bridge peripherals and the 

 hyoplastrals and hypoplastrals, and by axillary and inguinal buttresses. Heads of ribs, except 

 that of first costal bone, vestigial. Free borders of the peripherals acute. Scutes of the carapace 

 normal; most of the marginals rising and overlapping the lower ends of the costal bones. 

 Lobes of the plastron somewhat reduced; the hinder not notcht. Plastral scutes 7 pairs; the 

 intergulars excluding the gulars from contact on the midline. Inframarginals present. 



Type: Emys beatus Leidy. 



The genus Adocus, as here defined, is at present known only from Upper Cretaceous 

 species; and, except A. lineolattts, doubtfully referred to the genus, all are from the Upper 

 Cretaceous greensand of the eastern United States. Adocus may be regarded as the least 

 modified of the Dermatemydidae. Its advanct characters appear to be found in the slightly 

 reduced number of neurals, one or two of the most posterior probably being usually missing; 

 in the developt buttresses; in the aborted rib-heads; and in the reduced gular scutes. Prim- 

 itive characters are found in the possession of seven pairs of plastral scutes and the unin- 

 terrupted series of inframarginals. 



The following key may be of some value in separating the species: 



KEY TO SPECIES OF ADOCUS. 



A. Species of the Rocky mountain region; not well known lineolatus 



AA. Species of eastern United States region. 



a. Hinder lobe of plastron narrowed behind. 



b. Entoplastron wide; nearly equal to length of the suture between the hyoplastrals beatus 



bb. Entoplastron narrow; width nearly twice in the hyoplastral suture pravus 



aa. Hinder lobe broad behind; rounded or truncated. 



c. Gulo-humeral sulcus close to or crossing the entoplastron. 



d. Hinder lobe truncated behind; the length between three-fifths and 



four-fifths the width at the base functatus 



dd. Hinder lobe broadly rounded; its length three-fifths the width at the 



base; gulo-humeral sulcus just in contact with the entoplastron. . synthettcus 

 ddd. Hinder lobe broadly rounded; its length four-fifths the width at base; 



gulo-humeral sulcus well forward on entoplastron lacer 



cc. Gulo-humeral sulcus falling considerably behind the entoplastron agilts 



Adocus punctatus Marsh. 

 Plate 34, figs. 6, 7; plate 35, figs. I, 2; text-figs. 296-298. 



Adocus punctatus, MARSH, Amer. Jour. Sci. (3), XL, 1890, p. 178, plate vii, fig. 3. WIELAND, Amer. 



Jour. Sci. (4), xvn, 1904, p. 112, plates i-iv, text-figs. I, 2. 

 Adocus beatus, BAUR, Proc. Acad. Nat. Sci., 1891, p. 428. HAY, Bibliog. and Cat. Foss. Vert. N. A., 



1902, p. 444. 



At the present time this species is represented by better materials than any other of 

 the genus, and for that reason it is here described first of all the species of Adocus. The 



