8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 60 



passing - without a sharp line of demarcation into darker color of 

 sides, the fur everywhere darker and more plumbeous basallv ; ears 

 well clothed with dark hairs, whiskers grayish ; sides of rump with 

 a few projecting white hairs as in Ichthyomys hydrobates; upper 

 surface of metacarpus blackish ; metatarsus, including fringing 

 bristles, brownish ; toes of fore and hind feet dull white ; tail well 

 haired, black all round. Young (nearly full-grown) : Upper parts 

 nearly uniform mouse gray, lacking the cinnamon element of the 

 adult pelage. 



Skull. — Small and smoothly rounded, the frontal region not de- 

 pressed as in Ichthyomys hydrobates; audital bullae short and 

 rounded ; incisors of the ordinary murine type ; molars about as in 

 Ichthyomys hydrobates. 



Measurements. — Type: Total length, 201 mm.; tail vertebra?. 

 94; hind foot 23.5; ear from meatus (in dry skin), j.~. An 

 old adult topotype: 214; 102; 26.5. Skull (type): Greatest 

 length. 25.7; condylobasal length, 24.8; zygomatic breadth, 13.8; 

 nasals, 10.5 ; interorbital breadth, 5 ; interparietal, 7.3 x 2.7 ; in- 

 cisive foramina, 4.9 ; length of palatal bridge, 5.5 ; maxillary tooth 

 row. 4.2. 



Remarks.— Rlicomys raptor appears to be the smallest known 

 member of the Ichthyomys group. It may be not very unlike tri- 

 chotis which is still imperfectly known, but differs considerably 

 from the color description of the latter species. The upper incisors 

 are clearly of the Rhcomys type, the anterior surface not heavily 

 beveled internally as in Ichthyomys, in which the beveled internal 

 border results in the deep emargination of the cutting edge. The 

 whiskers are reduced to slender hairs, quite different from the stiff 

 bristles of Ichthyomys. 



Specimens examined. — Three, all from 4.500 to about 5,000 feet 

 altitude on the upper slopes of the mountains in the vicinity of 

 Mount Pirri. 



MACROGEOMYS DARIENSIS, sp. nov. 



Type from Cana (altitude 2,000 feet), in the mountains of eastern 

 Panama. No. 179587, male adult, U. S. National Museum (Bio- 

 logical Survey Collection), collected by E. A. Goldman, May 31, 

 19 1 2. Original number 21760. 



General characters. — Similar in general size to cavator, but tail 

 1' mger, color a duller brown or black, lacking the rich seal brown 

 shade of cavator; pelage shorter; whiskers and vibrissa? over orbits 



