88 



BULLETIN" 57, UNITED STATES NATIONAL MUSEUM. 

 Genus RHYNCHISCUS Miller. 



1823. Probosoidea Spix, Simiarum et Vespertilionum Brasil. Spec. Nov., 



p. 61. (Not ProTioscidca J. 6. Brugiere, 1791.) 

 1867. RUynchonyctcris Peters, Monatsber. k.' preuss. Akad. Wissensch., 



Berlin, p. 477. (Not Rhinchonycteris Tschudi, 1844-46.) 

 1878. Rliynchonycteru Dobson, Catal. Cliiropt. Brit, Mus., p. 366. 

 1904. ProDoscidea Allen, Bull. Amer. Mus. Nat. Hist., XX, p. 343, October 8, 



1904. 

 1907. Rhyncliiscus Miller, Proc. Biol. Soc, Washington, XX, p. <Ki. June 12, 



1907. 



Type-species.— Proboscidea saxatilis Spix=VespertiMo naso Wied. 



Geographic distribution.— The mainland of tropical America. 



Number of forms.— Only one species of Rhynchiscus is now known. 



Characters. — Dental formula : 



2 



1.-2-4567 .1-1 „ 1-1 



2-2 



m 



-3 



=32. 



1 2 3. 1. - 2 - 45"6 7 " 3 - 3' " 1 - 1' t "'" 2 - 2' "' 3-3" 

 Upper incisor minute, simple, persistent, inserted in main axis of 

 premaxillary and at extreme tip of bone, the 

 teeth, therefore, converging. Lower incisors 

 small, trifid, forming a continuous, slightly 

 concave line between canines. Canines and 

 lower premolars as in Emballonura. Anterior 

 upper premolar (pm 2 ) unusually large', its 

 crown sharply pointed and noticeably flat- 

 tened laterally, the outline being nearly an 

 isosceles triatfgle. First upper molar with 

 conspicuous antero-external cusp separate 

 from small parastyle. Hypocone of m 1 and 

 m 2 very distinct, subterete. Third upper 

 molar with well-developed metacone and 

 three commissures. Lower molars all alike 

 in form, the third merely smaller than the 

 others, all the cusps normal. Skull (fig. 13) with rostrum somewhat 

 more than half as long as brain case, and so' deep posteriorly that the 

 forehead forms scarcely any angle with upper surface of rostrum. 

 Lachrymal region slightly inflated. Premaxillaries short, very broad 

 posteriorly, extending to upper, surface of rostrum. Basisphenoid 

 pits deep, their outer border sharply defined ; but on inner side they 

 merge into each other without dividing ridge. Audital bulla slightly 

 larger than the two pits together. Mandible very abruptly bent 

 upward behind tooth row. Externally characterized by the greatly 

 elongated muzzle, and among the American genera by the absence of 

 wing sacs. The only known species has the forearm sprinkled with 



Fig. 13. — Rhynchiscus naso. 

 Adult male. Escondido 

 River, Nicaragua, 50 miles 

 from Bluefields. No. 51565. 

 X2. 



