50 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 9i 



A second lower jaw portion, No. 16255, collected in 1939, has P4 

 and the greater portion of Miand M2 preserved. P4 is a little shorter 

 than in most specimens of H. ongustus^ though relatively as wide and 

 appears inflated as characteristic of this genus. The two molar 

 portions show no important distinguishing characters. These two 

 teeth have the cingulum rather prominent external to the protoconid, 

 but distinctly weak on P4. In No. 15744 the cingulum is not evi- 

 dent. However, in H. angustus the development ,of the cingulum 

 appears to be highly variable, and when present is apt to be most 

 noticeable on the anterior portion of the tooth and about the hypocone. 



In 1940 several isolated teeth were found near one another at a level 

 about 30 or 40 feet higher than that of the Dragon fauna at the 

 old Dragon Canyon locality. These include P*, a right and left P4, 

 portions of two anterior lower molars, and the greater part of M3. 

 The talonid portions of the various lower molars are to be compared 

 with those of IJaploconus rather than any other known form. One 

 of the molars, however, has most of the trigonid preserved, and this 

 exhibits a small paraconid. It is also significant that the two lower 

 premolars have a moderately developed paraconid and are antero- 

 posteriorly elongate and slender, approaching the form seen in 

 Anisonchus, quite unlike the premolar exhibited in No. 16255 referred 

 to H. inopinatus. The form represented by these teeth is clearly 

 distinct from that represented by No. 16255, but I hesitate to describe 

 it as distinct because, first, there is no certainty as to which of the 

 types of lower teeth should be referred to H. inopinatus, and secondly, 

 there is no real assurance that the isolated teeth discussed above are 

 from one animal, although it seems probable that they are. , 



HAPL0C0NUS7 ELACHISTUS.^s new species 



Type. — Left maxillary portion with M^ and part of M% and lower 

 jaw fragments, U.S.N.M. No. 16191. 



Horizon and locality. — Wagonroad Paleocene, Dragon Canyon, 

 Emery County, Utah. 



Speciftc characters. — Size near that of Conacodon cophater, smaller 

 than either Haploconus angustus or Haploconus inopinatus. Teeth 

 relatively a little shorter anteroposteriorly than in H. inopinatus. 

 Difference between transverse diameters of M^ and M^ relatively not 

 so great. Protostyle weak. Lower molars and P4 with slight 

 paraconid. 



Description. — 'Representing Haploconus? elachistus are several iso- 

 lated teeth and a few jaw and maxillary portions with one or two 

 teeth. No. 16191, a maxillary portion with M^ and part of M^, and 



" 'tXixiCTToi, smallest or least, in allusion to size. 



