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Bulletin American Museum of Natural History. [Vol. XXXVII, 



even the darkest examples can be matched by numerous specimens from 

 the Congo region. The length of the forearm in the eight specimens from 

 British East Africa averages 31.7 mm. (30.3-32.3) as against 30.8 (29-31.5) 

 in 20 specimens from Bafwabaka, and 30.9 (30-31.9) in nine specimens from 

 Niangara, and 30 (29-31) in three adults from Stanleyville. The corre- 

 sponding measurement in the type and two topotypes of Pipistrellus aero 

 Heller is 31.3 (30.5-31.5), which specimens to me appear indistinguishable 

 from the British East Africa specimens labeled P. nanus. 1 



32. Pipistrellus abaensis sp. nov. 



Type, No. 48979, 9 ad.' (skin and skull), Aba, Belgian Congo, Dec. 18, 1910; 

 Herbert Lang and James P. Chapin. American Museum Congo Expedition. Orig. 

 No. 1825. 



Size of P. nanus, but much lighter in coloration, and with the sides of lower back 

 broadly naked. 



Upperparts light brown or pale isabella-color, the hairs nearly unicolor from base 

 to tip; underparts pale buffy gray, the basal portion of the hairs nearly black, the 

 tips light grayish with a slight buffy tone. Wing membranes attached to the entire 

 length of the basal joint of the outer toe. Ear small, pointed, about equally convex 

 on both borders. t 



Type, total length (collectors' measurements), 77 mm.; head and body, 44; 

 tail, 33; foot 7; ear, 10. Additional measurements from skin: Forearm, 31.4; 

 third metacarpal, 29.7; tibia, 12.4; foot, 6; ear 7.2. An adult female topotype is 

 larger: Total length (collectors' measurements), 84; head and body, 53; tail, 31; 

 foot, 8; ear, 12. Forearm (in skin), 32.1; third metacarpal, 30; tibia, 12.8; foot, 

 6.8; ear, 9. (The skull of this specimen, No. 48980, is lost.) 



Skull (type), total length, 11.7; breadth of braincase, 6.2; interorbital breadth, 

 3.1; maxillar breadth, 4.6; upper toothrow, 4; length of mandible, 8.1; lower 

 toothrow, 4.2. Incisors subequal in size, the inner one slightly bifid. P 2 exceed- 

 ingly minute, inserted on extreme inner edge of toothrow. 



Represented by 3 specimens, the type and two topotypes; both of the 

 latter lack skulls. Only two of the specimens, both females, are adult, one 

 slightly larger than the other, but both indistinguishable in coloration. 

 The third specimen is an immature male with the epiphyses not ankylosed 

 but nearly adult in respect to size. It differs from the others in the pelage 

 being nearly black above but somewhat lighter and more brownish below. 

 All three of the specimens agree in having the sides of the lower back naked, 

 the bare space being 5 to 6 mm. wide and 17 to 20 mm. long, extending from 

 the base of the tail membrane anteriorly for more than half the length of 

 the body. This feature, combined with small size, pale coloration and 



1 Received at the U. S. National Museum after the publication of Mr. Heller's description of Pipi- 

 strellus aero. 



