198 Bulletin American Museum of Natural History. [Vol. XIII, 



the Trinidad form here named M. chapmani, in honor of my 

 colleague Mr. Frank M. Chapman, to whom science is so deeply 

 indebted for his researches on the mammals and birds of Trinidad 

 is a very much larger animal than the true murina, and much 

 more deeply colored. Average male specimens of the latter have 

 a total length of about 305 mm., the head and body constituting 

 about 140 and the tail 165, as against 361, 171, and 190 for M. 

 chapmani. 



Marmosa klagesi, sp. nov. 



Type, No. 16121, $ ad., Ciudad Bolivar, Venezuela, Oct. 26, 1899 ; coll. 

 Samuel M. Klages, after whom the species is named. 



Above dull grayish brown with a dark rufescent tinge, the general effect 

 approaching dull russet brown ; space between the eyes but little lighter than 

 the crown ; dark loral spot enclosing the eye deep black, extending from the 

 base of the whiskers only to the posterior canthus of the eye, below the eye 

 reduced to a narrow line, but above the eye widening so as to occupy nearly one 

 third of the space between the eyes ; whole ventral surface pale yellowish white, 

 brighter on the chest, fore neck, and throat ; ears brown, much darker than in 

 M. murina ; fore feet pale yellowish brown ; tarsi dull brown, the toes much 

 lighter. 



Measurements, Total length of type, 325 mm. ; head and body, 155 ; tail, 

 170 (collector's measurements from the fresh specimen); ear (in dry skin) 16 x 

 . 14 ; hind foot, 18. 



Skull, in size and general form, much as in M. murina , but the supraorbital 

 bead is much more expanded laterally, forming an obtuse postorbital process. 

 Total length, 36.5 ; basal length, 31.5 ; nasals, 16.5 ; palate, 18.3 ; zygomatic 

 breadth, 20.5 ; mastoid breadth, 18 ; least interorbital breadth, 6.3 ; greatest 

 interorbital breadth, 8.6. 



Marmosa klagesi is based on three specimens, all males, two 

 of which are adult and the other about one third grown. The 

 young specimen scarcely differs in any respect in coloration from 

 the adults ; the pelage, however, is softer in texture, or less firm 

 and velvety. Even at this early age the skull shows an incipient 

 supraorbital bead. The species seems to be very distinct from 

 any previously described. It is smaller than M. chapmani, and 

 differs from it markedly in coloration and cranial characters. 



Thylamys keaysi, sp. nov. 



Type, No. 16068, $ ad., Juliaca, Peru, altitude 6000 feet, Jan. 8, 1900, 

 coll. H. H. Keays, for whom the species is named. 



