BUFFALO SOCIETY OF NATURAL SCIENCES 145 



tions. It is remarkable that the same two species should also be found 

 associated in the Conodont bed at Eighteen Mile Creek. 



We have 17 teeth of D. priscus, some of them in splendid preserva- 

 tion, showing the entire root, the median denticle and all the char- 

 acters of the species. These specimens enable us to add somewhat to 

 the account given by Eastman, who had available only imperfect 

 specimens. In the first place, it should be observed that there is con- 

 siderable variation in size among the teeth, some of the larger ones 

 being twice as high as the smaller ones. Secondly, the ornamenta- 

 tion, which consists of striae spiraling gently upward from base to 

 tip of tooth, varies considerably in the number and prominence of the 

 strife. Some teeth have seven or eight striae, others as many as a 

 dozen or more. Frequently short striae are interpolated between the 

 long ones in the basal portion of the tooth; or the striae may be 



Fig. s^- Dittodtis priscus 'Eastman. Three Teeth. Natural Size. E 1901 



A, a typical Dittodus tooth, i.e., with two large lateral cones and an intermediate 

 denticle. B, a tooth with the median denticle rather large and a minute denticle 

 between it and each lateral cone. This tooth is of the form usually placed in the 

 genus Phcebodus. C, a tooth with rather large median denticle but no minute den- 

 ticles between it and the lateral cones. This is also a Phcehodiis type of tooth. 



reduced on the posterior face, sometimes to only a few short ones con- 

 fined to the lateral margins. In all the specimens in hand, the central 

 portion of the posterior face is perfectly smooth. 



Eastman described the teeth as round in section. From our series 

 it appears that there was some variation in this regard; most of the 

 teeth are slightly compressed, and some at least, have sharp lateral 

 keels. There is also considerable variation in the height of the root, 

 as viewed from in front. In some teeth it is less than the height of 

 the median denticle, in others it is considerably more. The median 

 denticle varies greatly in size in different teeth; it may be quite small, 

 but generally it is large; in two or three examples it is nearly as large as 

 the lateral cones (fig. 51, C). There may be, too, minute denticles 

 between the medium and the lateral cones, producing teeth that if 

 found alone would undoubtedly be ascribed to the genus Phcebodus. 



