PERMIAN VERTEBRATES 705 



crests are present, all radiating in the same general direction, the longer 

 close to the inner border. There was not more than one additional crest, or 

 one and a rudiment, and these have probably the same direction as those 

 which are preserved. The crests are sharp, elevated, and coarsely dentate; 

 they are not decurved at the extremity, but cease abruptly- with a projecting 

 denticle, beneath which the basis is excavated by a shallow fossa. The 

 inferior face is slightly concave, the internal wall vertical." 



MEASUREMENTS. 



" Greatest width ------- .oo8 m 



Depth at inner border -__.-'. ,005 " 



[No. 6509.] 



Sagenodus pusillus Cope. Plate I, Figs, ga, gb. 



Ctenodus pusillus Cope, 1877, Proc. Am. Phil. Soc, p. 191. 

 (Pal. Bull., No. 26.) 



Sagenodus pusillus Woodward, 1 89 1 , Cat. Foss. Fishes Brit. 



Mus., Pt. II, p. 261. 

 Sagenodus pusillus Williston, Kans. Univ. Quart., Series A, 



p. 176. 



"Form narrow, the width of the base about equal to the depth. The 

 coronal portion is narrower than the base, because the inner face is oblique, 

 forming an acute angle with the inferior plane. There are but four crests, 

 of which the two longer are directed in one direction, and the two shorter 

 in another. The interior ones of both pairs form a continuous crest which is 

 convex inwards. The crests are straight, elevated and acute ; each one 

 supports two or three denticles, which are rectangular and little elevated. 

 The longer ones project beyond the general outline ; the shorter ones are 

 less prominent at the extremities ; all are obtuse in the vertical direction. 

 The superior surface is smooth. The inferior is slightly concave in the trans- 

 verse sense. The tooth on which this species is founded is the smallest yet 

 obtained from the formation (Permian of Illinois). Length, .007"' ; width, 

 .003 1 " ; depth at the inner crest, .oo3 m ." 



[No. 6508.] 



Sagenodus fossatus Cope. Plate I, Figs. 10a, 10b. 



Ctenodus fossatus Cope, 1877, Proc. Am. Phil. Soc., p. 54. 

 Sagenodus fossatus Woodward, 1S91, Cat. Foss. Fishes Brit. 

 Mus., Pt. II, p. 261. 



Sagenodus fossatus Williston, 1899, Kans. Univ. Quart., 

 Series A, p. 176. 



" Represented by a nearly perfect tooth of a general narrow and vertically 

 thickened form. There are five crests, the largest three extended in one 



