384 LONCHERES. 
molars with one internal and three external loops; lower molars with 
one external and two internal loops; mandible broad with conspicuous 
bead on inferior outline, the angle prolonged into a lengthened 
delicate spur; condyle broad, rounded at extremity; coronoid process 
short, pointed; symphyseal portion narrow, lower outline V-shaped. 
403. labilis (Loncheres), Bangs, Amer. Nat., Xxxv, 1901, p. 638. 
GLIDING SPINY Rat. 
Type locality. San Miguel Island, Bay of Panama. 
Genl. Char. Pelage long, stiff; spines wanting. 
Fig. Ll. LONCHERES LABILIS. GLIDING SPINY RAT. 
Color. Top of head, nose, and cheeks mixed black and yellowish; 
patch of yellowish white at base of whiskers, also one above eye and 
behind ear; rest of upper parts bright ferrugineous, varied with black 
in certain specimens; chin grayish white; under parts buff or ferru- 
gineous—in some individuals these colors show in patches; upper 
surface of hands and feet yellowish brown; nails white; tail at base 
like body, then black, tipped sometimes with yellowish white; ears 
blackish, nearly naked. 
Measurements. Total length, 420-540; tail vertebra, 175-240; 
hind foot, 42-48; ear from notch, 14-16. Skull: basal length, 47.8; 
occipito-nasal length, 56.6; zygomatic width, 27.4; mastoid width, 
22.4; interorbital constriction, 12; length of nasals, 16; width of 
nasals, 7.2; palatal length, to palatal notch, 21.2; to end of pterygoid, 
36.4; upper tooth row, 13; length of single half mandible, 34; lower 
tooth row, 13.2. 
The next is a comparatively large genus of moderate sized Spiny 
Rats. One curious characteristic of these animals is the tendency to 
lose their tails, the separation taking place at the fifth caudal ver- 
