1894.] 



NATURAL SCIENCES OF PHILADELPHIA. 



233 



Generic characters. — Upper molars much as in xVeotomo, '" hut 

 crowns of m ^ ami - with middle transverse loop divided hy 

 deepening of enamel fold on inner side; m ' and - with four 

 roots each ; m '^ with three roots ; lower molars with enamel folds 

 reaching about half- way across tooth ; m ^ shaped like letter S, 



Fig. 3. (x.5. ) a anil />. Hodnniys alloii. c and d. H. vctulux. 

 Xriioviys nclsoui. 

 a. c. r. Crowns of upper molars, b. d, f. Crowns of lower molars. 



and _/. 



with two salient and one re-entrant angle on each side, with a ten- 

 dency toward the subdivision of the antero- external loop by the 

 development of a notch (or vertical sulcus) on its convexity ; upper 

 incisors peculiarly excavated, apparently by the sharp point of the 

 lower ones, leaving a deep cavity behind the enamel face, which is 

 bordered laterally by the outer sides of the teeth. Cranium long 

 and narrow, much as in Neotoma pennsylvanica, only narrower ; 

 audital bullae small, abruptly narrowed anteriorly, the narrow part 

 produced obliquely inward, much as in Nectomys; inner side con- 

 spicuously excavated by the carotid canal and foramen, which is 

 considerably anterior to middle of bulla ; brain case narrow and 

 long; spheno- palatine vacuities closed; mandible with coronoid 

 notch more nearly vertical than horizontal ; condylar ramus high, 



'" Most of tlae accompanyins dcscri))! ion is drawn with reference to antithesis 

 with A'roloiiia. Prolmbly many of the characters a])ply to Pfyssoplioi-ux also, of 

 which animal, unfortunately, the craniinn and posterior part of the mandible 

 are unknown. 



