1902.] NATURAL SCIENCES OF PHILADELPHIA. 397 



There is niucli variation iu color, as pointed ont by Robinson 

 and Lyon. The young and a few adults are practically black. In 

 others Ihe rufous is more conspicuous than in the type, sometimes 

 invading the entire pelage to the exclusion of the dark brown. In 

 the completely red specimens the exact shade varies from burnt 

 umber to a rather dark tawny. 



Skull and Teeth. — The skull and teeth are much smaller than in 

 true Molossus rufiis, but I can detect no tangible difference in form, 

 beyond the rather less development of the sagittal and lamlidoid 

 crests. 



Measurements. — External measurements of type: Total length, 

 123; tail, 44; tibia, 18; foot, 11.4 (10.8); forearm, 45.4; thumb, 

 8.2; second finger, 42; third finger, 90; fourth finger, 70; fifth 

 finger, 47. 



Cranial measurements of type: Greatest length, 21 (23);'' basal 

 length, 18 (20); basilar length, 16 (17.4); median palatal length, 

 7 (7.2); interorbital constriction, 4 (4.2); zygomatic breadth, 13 

 (14) ; breadth of braincase above roots of zygomata, 10.6 (11.4) ; 

 greatest height of sagittal crest, 1.8 (3); mandible, (16.6); max- 

 illary toothrow (exclusive of incisors), 8 (8) ; mandibular toothrow 

 (exclusive of incisors), 8.8 (9). 



Specimens Exammed. — Seventy-one (44 skins), all from the 

 vicinity of La Guaira. 



Remarks. — Specimens from Sapucay, Paraguay, essentially 

 topotypes of Molossus rufus, which have been received within the 

 past few mouths, show that the bat from northern South America is 

 an easily recognizable form. The Paraguay skins are all a uni- 

 form reddish-brown, very near the raw umber of Ridgway. They 

 are very uniform in color and show no tendency to>vard the bright 

 tints of Molossus pretiosus in the corresponding phase. jSTeither is 

 there any suggestion of a black phase. As far as can be dete?'- 

 miued from the material now at hand, we have a large southern 

 form, true Molossus rufus, which apparently lacks the black phase 

 and in which the red phase is very dull; a large northern form, 

 M. nigricans, in which the red phase is rare, and a small foriii, 

 intermediate iu range, with both phases of pelage well devel- 

 oped and characterized by great richness of color. 



* Measurements in parentheses are those of an adult male Molossus 



rufus from Siipucuy, Piiragua}'. 



