Forms of Saimiri, Saccopteryx, &c. 253 



less than in B. infusca, though the skull is as large as in that 

 animal. General characters very much as in B. infusca ; 

 ears as in that species, the inner margin more evidently 

 concave just below the tip. Tragus slender, its tip rounded, 

 a marked lobule opposite to base of its inner margin, and 

 another slight projection higher up. Wing- and leg-bones 

 remarkably slender, much more so than in B. infusca. Wing- 

 sacs in the centre of the membrane, as usual in Balantio- 

 pteryx, about a quarter of an inch internal to a line drawn 

 directly forwards from the elbow. Feet quite free of mem- 

 brane, the wings attached to the distal end of the tibiae. 

 Calcars slender, not reaching upwards to the knee. Base of 

 interfemoral membrane hairy as far as the exsertion of the 

 tail. 



Colour of body above and below, and of membranes, dark 

 brown (in alcohol) ; no white line along hinder edge of wings. 



Skull agreeing in size with that of B. infusca, therefore 

 much larger in proportion to the size of the animal than in 

 that species. Muzzle flatter than in that species, and the 

 inflations smaller, though equally prominent ; in B. infusca 

 the two inflations meet in the middle line for about 2 mm., 

 while in B. io they are quite separate from one another, the 

 nasal region having a marked concavity between them, 

 bordered in front by an upturned edge above the centre of 

 the nostrils. Zygomata abruptly and widely expanded. 

 Front edge of palate with a well-marked median spine. 

 Posterior narial fossa widely open, its outline broadly 

 U-shaped. Basisphenoid pit large, more extended longi- 

 tudinally than in B. infusca, longer than broad, without trace 

 of median septum. Teeth apparently as in the allied species. 



Dimensions of the type (measured in spirit) : — 



Forearm 36 mm. 



Head and body 40 ; tail 1 2 ; tail free of membrane 4 ; 

 ear 12 ; tragus on inner edge 3 ; thumb 5'6 ; third finger, 

 metacarpal 31' 5, first phalanx 11, second phalanx 15 ; fifth 

 finger 36 ; tibia 14 ; lower leg and foot (c. u.) 22; calcar 10*5. 



Skull : greatest length 12*3 ; upper length in middle line 

 11*4 ; basal length in middle line 8"7; zygomatic breadth 

 8*8; breadth across muzzle 6 ; mastoid breadth 7*6; palate 

 length 3"3 ; basisphenoid pit 3 1 x 2*7. 



Ilab. K. Dolores, near Coban, Guatemala. 



Type. Adult male. B.M. no. 86. 9. 3. 1. Collected by 

 Mr. F. C. Sarg. Two specimens. 



These are the Guatemalan specimens referred by me to 

 B. infusca when describing that species, but there can be no 

 doubt as to their distinctness both in proportions and skull- 

 characters. 



