ART. 1. PRIMATES OF THE FORT UNION GIDLEY. O 



and basins shallow; protoconules present but less well defined than 

 P. maturus; metaconules absent. 



This species further differs from P. maturus in the slightly less 

 marked grooving of the inner wall of the protocone-hypocone shelf 

 and the relatively narrower proportions of p^ Differences correlated 

 with those just pointed out for the upper teeth are effected in the 

 lower teeth of the specimens here associated with this species, though 

 in somewhat less degree. The paraconids are weakly developed, being 

 almost vestigal on xa^ and m.^, and are closely connate with the meta- 

 conids, while the trigonids are more depressed although having the 

 same degree of forward slope as those of P. maturus. 



Several upper-jaw portions carrying teeth which conform very 

 exactly in size and general modifications with those of the lower series 

 seem to leave little question that they represent the same species. 

 One of these, a portion of a left maxillary carrying four teeth, p^ to 

 m^ (fig. 2, Cat. No. 9540), shows the following characters: Molars 

 wider than long with three main cusps and two intermediary cus- 

 pules, but, while there is no true hypocone, the base of the crown is 

 subquadrangular owing to a backward expansion of the base of the 

 protocone. This expanded area is distinctly marked off from the 

 protocone on the lingual side by a shallow, vertically directed depres- 

 sion, giving the impression of the birth of a hypocone. A low but 

 well-defined ridge, continuing from the posterior cingulum, slopes 

 abruptly upward to the summit of the 

 protocone, thus forming a second shal- 

 low posteriorly placed basin of almost 

 equal size and form with the one lying 



'^ "^ ° FlO. 3.— PAROMOMYS DEPRESSIDENS. POR- 



between the median conules. 1 hus the tion of a left lower jaw carrying the 

 ridge and cingulum function almost as three molars, croavn view, x 4/1. 



t 1 ^ ^ ■ V A CAT. NO. 9485. 



a hypocone and as already implied 



there is the suggestion of an early budding off of a mass from the 

 posterior flank of the protocone to form such a cusp. The modifica- 

 tion just described is more pronounced in m^ and m^, but is also 

 clearly indicated in m^, and p^ has a well-developed posterior cingu- 

 lum and ridge forming with the inner cusp (protocone) a similar basin 

 on this tooth. P* also has an incipient metacone placed well down 

 near the posterior extremity of the external cingulum. P^ and p^, 

 as indicated by their alveoli, are much smaller than p'' and are primi- 

 tively two-rooted; that is, the roots are antero-posteriorly placed. 

 The posterior border of the alveolus for the canine indicates a tooth 

 of moderate size; upper incisors not known. Length of upper cheek- 

 tooth series from posterior border of canine alveolus to posterior bor- 

 der of m^= 15.5 mm.; p^ to m^= 10.3 mm. Length of molar series = 

 7.8 mm. The infraorbital foramen and a short sector of the orbital 

 rim are preserved in this specimen, the latter indicating that the or- 



