14 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63. 



peculiarities to make them of interest, and they merit description, 

 although the lack of any clue to their association with other teeth at 

 present renders their reference too conjectural to be attempted. 



Among these there are three types, differing in detail but of 

 similar general form to those just discussed. The development of 

 lateral cuspulus suggests affinity to the Nothodectids, although ac- 

 curately associated material, when found, may show they belong 

 rather with some one of the other Primates having a single pair of 

 enlarged incisors, or possibly they are not Primate at all. This 

 seems to be true especially of the smallest of these three types. 

 This tooth (see pi. 3, fig. 10) is very minute and is of appropriate size 

 to go with the diminutive species Palaechthon minor to which I am 

 inclined to refer it for this reason. But, of course, correspondence 

 in size alone is no proof of relationship. It must be borne in mind, 

 however, that the material here under discussion came from a single 

 small area of but a few feet in extent, and was confined to a 

 stratum of an average thickness of not more than 4 inches. In 

 such intimate association, size often becomes the key to the solution 

 of proper specific association and sometimes even of individual iden- 

 tity of scattered anatomical parts. 



The little incisor, which I take to be an upper one (No. 10090, see 

 pi. 3, fig. 8) is relatively shorter crowned than the corresponding 

 Nothodectid tooth, but gives similar evidence of being one of a single 

 enlarged pair. The tooth is broken off near the base of the crown, 

 obliterating the evidence of whether or not it possessed a heel cusp, 

 but the normal presence of such a cusp is indicated by a sudden 

 increase in convexity of the posterior face of the crown base at the 

 point where it is broken. The crown consists of an elongated and 

 shghtly curved principal cusp with its anterior face strongly convex, 

 and with a small concavity near the summit on the external posterior 

 face. As in the Nothodectids, the incisors has two accessory cusp- 

 ules of unequal size but differently arranged, one being placed above 

 the other on the outer flank of the main cusp. 



Based on proportionate size there are two other suggestions of 

 species affihation for this tooth. The first is that it possibly belongs 

 to one of the small species of a multituberculate, remains of which 

 are abundant in the " Gidley Quarry" material; the second is that 

 it may appertain to a certain species of Insectivore, likewise well 

 represented, which agrees very nearly in size with the little primate 

 PalaecJiihon minor, the species to which I am more inchned to assign 

 it. Against the probabihty of the Insectivore association is the fact 

 that in none of the families of that group is there any species, known 

 to me, possessing enlarged upper incisors in which the crown has 

 developed lateral cuspules. The Sorecidae, as noted by Matthew, 

 have reduced the number to a single enlarged pair, with elongated, 



