438 PROCEEDINGS OF THE ACADEMY OF [April, 



lobe low; internal connecting membrane rather high, with a slight 

 median emargination. Nose-leaf acute; nose-pad with the inferior 

 margin more or less free; nostrils crescentic. Pad on the lower jaw 

 trigonal, median incision of varying depth, but usually rather Inroad 

 and shallow. 



Limbs. — Forearm long and heavy, with a distinct and even arcuation. 

 Posterior limbs moderately robust (for the genus) , femora and tibise of 

 equal length ; foot about half the length of the femur, rather heavy ; 

 calcaneum thick and flattened. Tail rather long, one or one and a 

 half terminal joints free. 



Membranes and Fur. — Essentially as in the waterhousii group. 



Color. — Two color phases are present in the series examined — one 

 dark brown the other of a more rufescent type — between which two 

 extremes arc a number of intermediate specimens. Dark browTi phase : 

 Above bistre with a slight overlying silvery ''bloom," the basal three- 

 fifths of the hair white; below wood brown, the hair Avith the basal 

 section as above, the whole with the tips of the hair white; hair at 

 the base of the ears and the auricular hairs whitish; membranes bistre. 

 Rufous brown phase: Above cinnamon, slightly more than the basal 

 half of the hair white ; below the hair white basally, then ringed with 

 cinnamon, and tipped with ecru drab, thus producing a paler color 

 than that of the upper surface ; hair at the base of the ears and auricular 

 hairs whitish; membranes mummy brown. 



Skull. — Similar to M. ivaterhousri, but slightly smaller, with the inter- 

 orbital region more depressed and the rostrum slightly slenderer. 



Teeth. — As in ilf. waterhousii. except that the canines are distinctly 

 weaker, the first upper premolar is more compressed, the second upper 

 premolar slightly longer, and the lower tooth-row more compressed. 



Measurements. — Average of four Cuernavaca specimens: Total 

 length 93.1 mm. (87-101); head and body 59.8 (56.5-64); head 24; 

 ear 25.2 (24-27); greatest width of ear 17.7 (17-18.5); tragus 9.2 

 (9-9.6); forearm 49.6 (47.5-51.5); thumb 12.5 (11.5-13); third digit 

 87.1 (85.5-90); tibia 21.2 (21-21.5); calcaneum 10.3 (9-11.3); foot 

 12.7 (11.8-13); tail 33.5 (30-37). 



Average of eight Tehuantepec skins : Total length [1] 100.5 mm. ; head 

 and body 60.9 (57-69) ; head [1] 29.2; ear 26 (24-28.5) ; greatest width 

 of ear [3] 18.8 (17.9-19.5); tragus 8.5 (8-10); forearm 52.5 (51-53.5); 

 thumb [7] 12.3 (12-13.5); third digit [5] 87.8 (87-89); tibia 22.2 

 (20-23.5); calcaneum 10 (9-11); foot 13.1 (13-13.5); tail [1] 31.5. 



Average of eight skulls from Tehuant(>pec and Reyes, Oaxaca: Total 

 length 24.8 mm. (24-25.5); greatest zygomatic width 12 (11.5-12 5); 



