SYSTEMATIC REVISION 



17 



Teeth broader; median cusp wedge-shaped, extending across the crown; internal 

 and external cusps nearly equal in size and separated by a considerable area from 



the median cusp. 



Diadectes biculminatus Cope. (Plate 1, tig. 4.) 



Diadectes biculminatus Cope, Proc. Am. Phil. Soc, vol. xxxv, 1896, p. 132. 



Specimen No. 2 of Diadectes sideropdicus, Proc. Am. Phil. Soc, vol. XVII, 1878, p. 505. 



Type: A fragment of a mandible with two complete teeth. No. 4374 Am. Mus. 

 Nat. Hist. Cope Coll. From Texas. 



Original description: The teeth are "remarkable for their compressed form, 

 and for the unequal elevation of the grinding surface. There is a median cusp 

 much elevated above an external heel, which is at the base of the crown; and there is 

 an internal cusp which is fused to the median cusp, and reaches a similar elevation. 

 It is doubtful whether there are any interalveolar walls, as the teeth are closely 

 placed. The internal cusp is a little more elevated than the median, and its apex 

 is separated from that of the latter by a shallow notch. The outer wall of the median 

 cusp is vertical, while the inner wall of the inner cusp is convex both vertically and 

 anteroposteriorly. The worn section of the two is unequally dumbbell-shaped. 

 The external face of the median cusp exhibits a median rib, with a groove on each 

 side, besides finer grooves, which are also present on the anterior faces of the crown 

 near the external border. Internal to these, the median cusp sends shallow grooves 

 obliquely inwards and downwards, which do not reach the base of the internal cusp. 

 The transverse diameter of the crowns diminishes gradually posteriorly, so that the 

 alveolus of the last one of the series is small and round. * * 



"Measurements. M 



"Length of series of nine teeth °-°4 6 



Width of crown of largest molar 0I 3 



Elevation of external heel 00 5 



Elevation of internal cusp 0I1 



Anteroposterior diameter °°a" 



Width of mandibular ramus at do ° 2 " 



Revised description: The teeth are narrow anteroposteriorly, with the inner end 

 slightly wider than the outer. The outer cusp is very low, and the median and inner 

 cusps (of equal height) are much more elevated than the outer. 



Diadectes fissus Cope. (Plate 1, figs. 1, 2, 2a.) 

 Proc. Am. Phil. Soc, vol. xx, 1883, p. 634. (Also Pal. Bull. 36.) 

 Proc. Am. Phil. Soc, vol. xxxv, 1896, p. 132. 



Type: Two individuals. A maxillary with dentition and a fragmentary skull, 

 No. 4348 Am. Mus. Nat. Hist. Cope Coll. From Texas. 



Original description: "Superior teeth wider, 14 on each side, the last the largest, 

 sphenoid not keeled." "The Empedias fissus is nearest the E. molaris and has the 

 same number of teeth. It differs, however, in various essential points. The last 

 maxillary tooth, which is much reduced in size in the E. molaris, is here as large as 

 any of the others. The portion of the crown within the median cusp is fissured 

 medially in the direction of its length; that is, transversely to the axis of the jaws. 

 This fissure is not so distinct in the mandibular teeth. The median cusp has a 

 straight edge at right angles to the long axis of the crown. The specimens where 

 the entire dental series of one side is preserved shows that the latter has a sigmoid 

 flexure, the middle of the maxillary bone being incurved, and the anterior part being 

 convex outwards. There are five or six conic teeth between the incisors and the 

 molars. * * * 



