6 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63. 



bit was large but relatively not so forward in position as in Tetonius. 

 The infraorbital foramen is large, narrow oval in outline, and placed 

 directly above the junction of p^ and p^ 



PALAECHTHON, new genlis. 



Genotyije .—Palaeclithon alticus'pis, new species. 



1 % ^ 'i 



Diaqnosis. — Dental formula: I — ^ — , c -, p — '- — , m -: Lower 

 ^ 1 or 2 1 2 or 3 3 



incisors reduced to a single enlarged pair, as in Paromomys. Canines 

 unreduced, premolars three to two; molars differing from those of 

 Paromomys in having relatively shorter basins, and the heel of m.^ is 

 less widened posteriorly; there is no connecting ridge between the 

 subequal proto and meta conids, and the much-reduced but distinct 

 paraconids of m^ and m3 are not connate with the metaconids, but 

 are placed well down on the anterior borders of these cusps. The 

 upper dentition is only known from the molar series. These teeth 

 much resemble the corresponding ones of Paromomys but may be 

 distinguished by their less expanded inner bases and in consequence 

 more nearh^ trigonate form. The tendency to division of the lingual 

 wall of the protocone, so characteristic of Paromomys, slightly indi- 

 cated in m^, but is not present in the other molars. 



PALAECHTHON ALTICUSPIS, new species. 



Plate 1, Figure 1. 



Type. — Portion of a right lower jaw carrying five teeth, pj to va^. 

 CoUected by A. C. Silberhng. (Cat. No. 9532, U. S. N. M. Coll.) 

 Represented in the collection by other specimens including upper 

 jaws. 



Locality and horizon. — Same as Paromomys maturus. 



Specific characters. — Slightly smaller than Paromomys depressidens. 

 Pj to m2 = 9 mm., posterior border of canine to nij (estimated) = 11.5 

 mm. Premolars three, the anterior two reduced and simple; trigo- 

 nids of molars relatively higher and less forwardly directed than in 

 the Paromomys species; cusps of the trigonids very distinct, with 

 deep notches between the subequal protoconid and metaconid, and 

 with small paraconids on all of the molars depressed well below the 

 summit of the metaconid. The heel of m3 is relatively narrower and 

 is not distinctly biscusped, and the talonid basins of all the molars 

 are distinctly deeper than in the other species. These basins, how- 

 ever, are almost entirely open on the lingual side, there being but a 

 low and deeply notched ridge connecting the entoconid with the 

 metaconid. In Paromomys this ridge is nearly as high as the outer 

 border of the basin. P^ of P. alticuspis is more progressive than in 

 the species of Paromomys, it having a well-developed though short 

 heel and a rudimentarv but distinct metaconid. 



