70 AMERICAN MESOZOIC MAMMALIA 



Type species small, but mandible rather closer to that of Laolestes than of Amblothe- 

 rium. 



Type. — Kefolestes color adensis Simpson. 



Distribution. — Morrison formation, Colorado. 



The dinosaur quarries at Garden Park in the southern Colorado foothills yielded 

 three jaws to Professor Marsh's parties. Two are badly preserved docodontids, prob- 

 ably Docodon sp. nov., and this is the third. These are of great interest as being the 

 only American Jurassic mammals not from Como BlufiF. The present specimen, al- 

 though imperfect, is also of much interest as presenting what is clearly a new variant 

 of the rather stereotyped dryolestid molar pattern. It is probable that this material is 

 not of exactly the same age as that from Como Bluff, but at present it is not possible 

 to achieve an exact correlation of the various Morrison faunules. The fact that the 

 present genus is not known at the more northern locality may be due to the geographic 

 separation, to slight difference of fades, or (but less probably in view of the large 

 number of specimens from Como Bluff) to accident of collecting. Its generic characters 

 are not such as would indicate a form ancestral to or derived from those just described, 

 and hence it is of no immediate value in exact age determination. 



Ke-polestes coloradensis Simpson 1927 

 1927. K. coloradensis, Simpson, Amer. Jour. Set. (5) XIII, 413. 



Type. — U.S.N.M. No. 2723. Right lower jaw in matrix, inner aspect, with P4 

 and Mi-8, mostly somewhat broken. 



Horizon and Locality. — Morrison formation. Garden Park. 



Diagnosis. — Sole species of the genus. Total length of molar series ca. (i.2. mm. 



Dentition 



Only enough of the last premolar remains to show that it was a high, somewhat 

 recurved tooth about twice as high as the molars. The latter are all of about the same 

 size. The vcvt^ is blunt, truncated, but not bifid. The paraconid curves forward and 

 upward, leaving a rounded, U-shaped notch between it and the me''. On M 7 it rises 

 quite as high as the me'', but it was probably a little lower on the preceding teeth. The 

 pa'' and talonid cusp are in line with the me'', as in Dryolestes and Amblotherium, not 

 slightly internal to it as in Laolestes. 



Mandible 



The mandible recalls that of Laolestes save for its smaller size. The internal 

 groove is much as in other dryolestids, and the symphysial surface is long and nar- 

 row. The alveolar border, in internal aspect, is nearly straight and the lower border 

 forms an evenly convex curve, lowest beneath Me. 



Measurements 



Lengths : Depth of ramus be- 



Mi.g M3 M4 Mb Mg M7 low Mg, inside 



ca. 6.2 0.7 0.7 0.7 0.7 0.7 2.2 



