510 PHTLLOSIOMID^. 



other in the large size of the interfemoral membrane, but also differs 

 from it as remarkably in the form of the skull and teeth (see Plate 

 XXVII. figs. 6, 6 a, teeth of Gh. minor). 



Synopsis of the Species. 



a. Calcaneum shorter than the foot; forearm 



l"-7 1. Ch. mexiemia, p. 510. 



b. Calcaneum longer than the foot; forearm 



l"-35 2. Ch. minor, p. 511. 



1. Choerouycteris mexicaua. 



Chceronycteris mexieana, Tschudi, Fauna Peruana, p. 72, pi. iii. fig. 3 

 (1844) ; Peters, MB. Akad. Berl. 1868, p. 366. 



Muzzle longer than in any of the preceding species ; ears as in 

 Glossonycteris geoffroyii, but less than half the length of the head 

 (Plate XXVII. fig. 5, head and tongue). 



Thumb shorter than the foot; wing-membrane extending to the 

 ankles or tarsi; interfemoral membrane weU developed, extending 

 almost as far back as a line drawn between the ankles, the posterior 

 margin concave behind ; tail about one third the length of the in- 

 terfemoral ; calcaneum shorter than the foot. 



Fur, above, dark brown, the base of the hairs light greyish brown ; 

 beneath, light brown ; on both surfaces moderately long and dense, 

 but scarcely extending to the membranes ; the extremities and the 

 interfemoral membrane, above and beneath, naked ; the head clothed 

 with short fur, but the extremity of the muzzle around the nose- 

 leaf and chin beset with long straight hairs. 



Upper incisors very short, the outer incisors slightly larger than 

 the inner ones ; lower incisors deciduous ; first upper premolar de- 

 ciduous, the second separated by a wide space from the canine ; the 

 second and third premolars narrow, triangular, acutely pointed, equal 

 in vertical extent, without basal cusps ; first upper molar very 

 narrow, triangular in cross section at the base (the vertex of the 

 triangle being posterior), the outer cutting side without trace of W- 

 shaped cusps, but with a longer anterior and shorter posterior tu- 

 bercle ; second upper molar slightly broader at the base, third simi- 

 lar ; all the premolars and molars separated by spaces ; first lower 

 premolar close to the canine and separated from the next tooth by a 

 space equal to half its length, larger than the second or third pre- 

 molar, nearly as deep in front and behind as in the centre ; second 

 and third premolars nearly equal in size, each with a central acute 

 cusp and a smaller basal cusp in front and behind ; third premolar 

 as far from the first molar as the first premolar is from the second ; 

 molars equidistat and nearly equal in size, the second slightly 

 broader than the other two. 



Length, head and body 2""6, tail 0"'25, interfemoral membrane 

 about 0"-7, head l"-25, ear 0"-6, tragus 0"-25, nose-leaf 0"-25, 

 forearm l"-7, thumb 0"-35; third finger — metacarp. l"-6, 1st ph. 



