NATURAL SCIENCES OF PHILADELPHIA. 285 



brane in the Memoir, loc. cit., is taken from a young specimen ; and the ac- 

 count is otherwise too meagre. It is unfortunate that the original specimens 

 of this bat, recorded in the Memoir, are unavailable for comparison. They 

 were mislaid during the fire at the Smithsonian Institution in January, 1865, 

 and have not since been found. 



II. 



RHOGEESSA, n. g. 



Skull. Depressed, not crested ; occiput triangular, slightly swollen, supra- 

 occipital process subtrenchant. Nasal bones slightly decurved, in median 

 line forming a conspicuous linear fossa running to the nares ; superior 

 border of anterior nares rounded, not reaching line of infra-orbital foramen 

 above ; on palatal surface terminating on a line with the premolar. Orbital 

 processes but slightly swollen, lower than base of nasal bones. Sides of face 

 between these points concave, groove-like. Inner wall orbital space acutely 

 convex, incurved markedly at base. Infra-orbital ridge defining foramen be- 

 hind ; foramen on a line with first true molar ; cochleas not visible ; intermax- 

 illaries rudimentary ; lower jaw ramal angle rather broad, turned outward 

 from angle. 



Dental formula 



i. c. m. 

 1 1 4 = 30 



3 15 



Molars as in Nyctkejus; lower premolars closely approximated; canines above 

 with a groove on palatal face deeper inferiorly, terminated by a cingulum ; 

 lower cingulum marked ; incisors above close to canines, slender, convergent, 

 unequally bifid at tip ; inner cusp the longer. Below, terminal tooth on either 

 side unicuspid ; remainder tricuspid ; external cusp inconspicuous. Ear 

 tapering, erect, disjointed, nearly as long as head ; internal basal lobe 

 rounded ; external basal almost null ; border inverted. Tragus erect, subu- 

 late, half height of ear, straight on inner, divergent on outer border ; basal lobe 

 comparatively small. Snout obliquely truncate or slightly tumid ; nostrils 

 circular, well defined, terminal, separated by a slightly scalloped space. 

 Mental plate obscurely triangular ; distal joint of thumb free ; wing mem- 

 brane to base of toes ; ex-calcaneal lobe present ; joints of tail eight, included 

 in a nearly naked triangular inter-femoral membrane.* 



R. parvdla, n. s. (No. 7841 type.) 



Ear sub-acute at tip ; lips whiskered ; eyes very small, each furnished with 

 a wart above ; similar growth seen beneath chin. Fur above silky, not thick, 

 of a light greyish-brown at basal third, fawn-chestnut-brown at apical two- 

 thirds ; that of head same color, running on to the ears one-half their height. 

 Beneath, basal third inclined to greyish ; apical two-thirds greyish-fawn. 

 Membranes almost black, naked, excepting basal fourth of interfemoral mem- 

 brane behind, which is furnished with a small, short patch of glistening fur. 



Compare 

 Ntcticejus (N. crepuscularis). 



Skull slightly depressed at vertex ; occiput obtusely triangular, entire, not swollen ; nasal bonea 

 flat, with a small shallow median fossa, not running to nares, which are irregularly rounded at 

 upper border, extending to level of infraorbital foramen ; on palatal surface broad, running to level 

 of premolar. Orbital processes acutely edged, inner wall orbit nearly fiat. Infra-orbital ridge and 

 foramen as in Rhogeessa, but no oblique groove on sides of face. Cochleas not visible. Lower in- 

 cisors all equally trifid; upper incisors unicuspid. 



Ntctinomus (N. nasutus). 



Skull much depressed at vertex. Occiput not completely defined, rounded, and swollen at supra- 

 occipital region. Nasal bones fiat, scarcely decurved, a small fossa seen at their base, and convex 

 at nares. Contour of anterior nares above obscurely tri-foil like, extending to level of infra-orbital 

 foramen, small on palatal surface running to level canine tooth. Orbital process swollen, poste- 

 riorly produced in front. Infra-orbital foramen at posterior third of orbito-nasal space. Inner 

 wall orbital space flat. Cochlea not visible. Upper incisors unicuspid; lower centrals bifid; 

 laterals unicuspid. 



1866.] 



