56 SINCLAIR— THE SMALL ENTELODONTS 



It is evident from the above that small forms w^ith reduced m^, in 

 some of which the lower anterior premolars are closely crowded, have 

 a wide range both in space and time, and it will, accordingly, be 

 advisable to look into the matter of their relationship with both 

 ArchcBotherium coarctatum and A. niortoni. All of the specimens to 

 which I have referred are perfectly typical Archceotherium, differing 

 from Entelodon in the triangular crown and notched anterior border 

 of the fourth upper premolar, the spacing between the upper pre- 

 molars anterior to p^, the absence of greater width in the posterior 

 part of the crown of p^ and the presence of distinct para- and meta- 

 conids in the lower molars, where preserved in association with the 

 skull. In view of the comparisons to follow it is a fair presumption 

 that the Cypress Hills form, from its resemblance to the South Da- 

 kota and Nebraska skulls in the matter of crowded lower premolar 

 dentition and other features, should properly be referred to Archcso- 

 therhim, rather than to Entelodon. 



A. coarctatum is based on a left mandibular ramus with all the 

 teeth except incisors and canine, and the following characters are 

 either specified by Cope or may be deduced from his figure.^ Com- 

 parison will be made with the newly discovered material, with crowded 

 lower premolar dentition, as we proceed. 



1. A. coarctatum differs from all other small entelodonts so far 

 described in the absence of diastemata between the lower premolars, 

 except for a very short one between the first and second, resembling 

 the Bear Creek specimen in this respect, where the diastema is some- 

 what longer, due to the greater size of the individual and differing 

 from the Hat Creek skull (No. 1481, Am. Mus.) in lacking the small 

 inconstant spacing between p^ and pg. 



2. The first lower premolar is separated by a very short space 

 from the canine, also true of these specimens. 



3. The third premolar is larger than the fourth and the first and 

 second are abruptly smaller than either of the others. P3 was cer- 

 tainly the largest in the Bear Creek specimen (Princeton 12624), with 

 P2 not much shorter than p^, judging from the extent of the empty 

 alveoles. In the skull from Hat Creek the teeth have proportions 



3 Loc. cit., PI. XIV., Figs. 3, 2,a. 



