4:40 E.L, T voxel] — Enteloclonts in Marsh Collection. 



P 4 in its general form resembles that tooth in Ammodon 

 leidyanus in that its single. cusp is evenly rounded, 

 minutely striated, and has a strong ridge leading from the 

 apex to the broad, roughened, shelf -like heel inclosed by 

 a strong cingulum. A. leidyanus differs in having two 

 ridges and many tubercles on the posterior heel, and in its 

 much greater size ; the diameter anteroposterior is 53 

 mm., transverse 33.5 mm. Of M. latidens, anteropos- 

 terior 44 mm., transverse 29 mm. 



The lower molars at once distinguish themselves by 

 their great size, much greater width, the wide open val- 

 leys, the smaller tubercles of uniform height, and the 

 equality in size to each other. 



The first lower molar has a double cusp on the meta- 

 conid (paraconid and metaconid combined?), making it a 

 little larger than either the proto-, ento-, or hypoconid, 

 which are about equal in size. The anterior cones are 

 rather close together, while the small entoconid is sepa- 

 rated by a wide valley on both sides. There is a double 

 cingulum anteriorly and a strong heel posteriorly; a 

 sharp valley exteriorly between the proto- and hypoconids 

 leads down to a circular cusp or basal pillar which does 

 not appear markedly on the second or third molars. M, 

 is wider posteriorly than anteriorly (35 and 32.5 mm. 

 respectively) ; its length is 39.6 mm. 



The four cusps of M 2 form a rectangle ; the metaconid, 

 almost a single cusp, is largest, while the entoconid is 

 slightly smaller than the two others. The valley between 

 the anterior cones is wide but not deep, the transverse val- 

 ley is deeper and narrower at the bottom; the area be- 

 tween the posterior cusps is broad, shallow, and rough- 

 ened. There is an enlarged cusp on the heel. 



M 3 has even broader valleys, and because the entoconid 

 is so small, the posterior half of the tooth is broad and flat. 

 A small cusp constitutes the heel. As in M 2 , there is a 

 double cingulum, anterior. 



This tooth is totally different in structure from M 3 of 

 Pelonax bathrodon, which has very high anterior cusps, 

 and from the paratype of A. leidyanus, which has very 

 sharp valleys and long posterior cusps. 



As to the geological age, we have to depend upon a 

 statement in a letter from L. W. Stilwell, dated April 20, 

 1889, referring to this specimen, in which he says it "was 



