THE' FAMILIES AND GENERA OP BATS. 191 



Geographic distribution. — Tropical America, north to Honduras. 



Characters. — Shoulder joint and wing as in the Natalidse, except 

 that trochiter is distinctly larger than trochin, second finger is re- 

 duced to a rudimentary metacarpal less than half as long as that of 

 third finger, there are three bony phalanges in third digit, and first 

 phalanx of thumb bears a large sucking disk ; shoulder girdle differ- 

 ing from that of the Natalidas and resembling that of the Furi- 

 pteridas in the small size of the presternum, its width scarcely half 

 length of presternum and mesosternum, its narrow keel slanting con- 

 spicuously forward, mesosternum broad and flat, its keel obsolete, 

 xiphisternum long and slender, its keel reduced to a mere ridge ; first 

 and second dorsal vertebra; fused ; foot abnormal, the toes with only 

 two phalanges each, the third and fourth digits, together with their 

 claws, anchylosed together from base to tip; fibula reduced to a 

 minute osseous thread closely applied to the tibia and disappearing 

 about midway between heel and knee ; sole with well-developed suck- 

 ing disk attached to metatarsals; pelvis not essentially abnormal, 

 but with very small pectineal process, and with obturator foramen 

 much reduced by bony outgrowth from its sides, as in the Hippo- 

 sideridse and Bhinolophidse, ischia wide apart posteriorly, a sym- 

 physis pubis in males, sacrum with the posterior two vertebras dis- 

 tinct, the others fused; lumbar vertebrae distinct; skull without 

 postorbital processes, much as in the Natalida;, the braincase large, 

 smooth, and rounded, the rostrum slender and weak; premaxillaries 

 complete, the very slender and easily broken palatal branches isolat- 

 ing two foramina; teeth normal, not essentially different from those 

 of the Natalidee ; ear, tragus, and muzzle as in Natalus. 



History. — As shown by the synonymy, this family has generally 

 been united with the Vespertilionidas or Molossidae. Winge placed 

 it with Natalus, Furipterus, and Amorphochilus to form the group 

 Natalina, a section of the Vespertilionidas ; and this assemblage I 

 regarded in 1899 as constituting the family Natalidce. 



Remarks. — The form of the sternum, the separate lumbar verte- 

 bra?, the greatly reduced second finger, the large third finger with 

 fully ossified terminal phalanx, the peculiar structure of the toes, and 

 the presence of sucking disk on thumb and sole are sufficient to dis- 

 tinguish this family from the Natalidae. Contrary to what might be 

 expected, the thumb has a well-developed claw. The Thyropteridas 

 are in some respects more highly specialized than the Natalida?; in 

 others, notably in the structure of the sternum and in the unfused 

 lumbar vertebras, much more primitive. As compared with the 

 Furipteridse this family represents about the same stage in the devel- 

 opment of the sternum; the lumbar region is more primitive; the 

 feet are more highly modified, and the thumb is perhaps equally 

 aberrant, though in another way. 



Principal subdivisions. — The family is represented by the single 

 genus Thyroptera. 



