BUFFALO SOCIETY OF NATURAL SCIENCES 147 



with the description and figures of the type, we do not hesitate to refer 

 ij: to D. striatus. 



E 2491 A complete tooth. Total height, 5.5 mm.; width of jaase, 

 6; antero-posterior diameter of base, 4.5. 



Conodont bed, (Genesee), Eighteen Mile Creek, near 

 North Evans, Erie County, N. Y, Collected by W. L. 

 Bryant. 



Dittodus grabaui, n. sp. 



(Text-fig. 52) 

 E 1910 Cofypes. — Five small teeth, free of matrix. 



Formation and Locality. — Conodont Bed (Lower Genesee) ; Eighteen 

 Mile Creek, near North Evans, Erie County, N. Y. Collected by 

 W. L. Bryant. 



Teeth small, 2 to 3 mm. in height, with two or three principal cones, 

 and usually a minute denticle between the median and each outer 

 cone. All cones perfectly smooth, without striations on either the 

 inner or outer face. Root, viewed from in front, broader than high, 

 its height to base of median denticle slightly less than height of outer 

 cones; expanded downward at external margins; a "button" present. 



Remarks. — Of this species we have a series of about 50 teeth. 

 Although unquestionably all of one species, they show considerable 

 variation in the size and number of denticles, so that one may arrange 

 them into a progressive series leading from Dittodus at one extreme, to 

 Phoehodus at the other. The first stage (fig. 152, ^4) is a typical Ditto- 

 dus tooth with two principal cones and a smaller denticle between 

 them; the next is a stage with the median denticle somewhat enlarged; 

 the next (fig. 52, C) is like the preceding but with a minute denticle 

 between the median cone and each of the outer cones. Finally we 

 have a tooth (fig. 52, £) with three principal cones, the median one 

 being also enlarged, and a pair of minute denticles between the median 

 and each of the outer cones; in other words a Phoebodus tooth. (Not 

 as well shown in figure 52, E, as in some other specimens in the 

 collection.) 



This series demonstrates clearly that Phcebodus merges into Dittodus. 



From the studies of Fritsch,^'* also, it is known that in the Pleura- 



^* Fauna der Gaskohle und der Kalksteine der Permformation Bohmens, vol, iii, pi. xciv, fig. i (Pleura- 

 tanthus parallelus Fr.), 1895. 



