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320 BULLKllN :!1, UMTKl) STATES NATIONAL MfSKUM. 



Vt'itebni' procaOoiis. Sacral diapopliyses dilated, the simple iirostyle 

 articulated to two condyles. External nietacariu bound tof^etlier. Ter- 

 minal phalanges articulated inleriovly onto the extremity of the penulti- 

 mate, globular or swollen proximally, and giving rise, usually from a cen- 

 tral emargination, to the curved, acute distal portion, which is of a more 

 compact tissue. Superior plate of ethmoid never covere«l by ironto- 

 l»arietals, usually produced anteriorly between frcMitonasals. Ear per- 

 fectly developed. Abdominal integument generally areolate. 



Tills family embraces the tree toads of Australia and America. It 

 presents comparatively little structural variety, not containing as un- 

 developed types as the Cystiguathida', nor as high ones; it poss.esses 

 neither earless nor fossorial, nor really acjuatic genera. 



The adaptive modifications are: First, those which accompany a ter- 

 restrial habitat, i.e., the diminution of the digital dilatations and palma- 

 tiou. These occur in regularly increasing degree in a small nnnd)er of 

 the species of the typical genus llyla, and are general in atul distinctive 

 of two other genera. Second, those whiiili adapt the extremities to 

 grasping a limb by opposition of digits, instead of adhering to a sur- 

 face by expansion of them in one plane. This lirst appears possible in 

 Agalychnis, and is structural in IMiyllomcdusa. Third, those which re- 

 strict the light admitted to the retina, first, by the lateral contractility of 

 the pupil; second, by the ren<lering opaqueof the inferior palpelira. The 

 lirst characterizes the two genera just mentioned, the last occurs in the 

 first two, but is inconstant in the second, and characterizes two other 

 genera. Fourth, that which adaj»ts the female dm iug the breeding sea- 

 son to localities without water, or where peihap.-i the water (;ontains 

 enemies, by the inversion of the dorsal integument so as to lorm a sacli, 

 in which the eggs are carried. This occurs in and is accepted as char- 

 acteristic of two genera. 



Another feature, which has a functional value, is the union of the 

 abdominal integnmenls with the snperlicial fascia of the muscles by 

 an areolar or (ibrous network, continuous with that of the usual latero- 

 ventral band. The skin of the inferior surfaces of these creatures, as in 

 the raiiiform tree frogs, has a thickening in numerous close areola', the 

 nature and fun(;tion «)f which is like that of the digital dilatations, and 

 Ihevlerm of the tuber on the thumb of the male K'ana, /. <■., to secrete an 

 adhesive fiui:l as aid in maintaining the peculiar positions assumed. 

 In proportion to the development of these is the extent ol' the abdomi- 

 nal attachment, and hence may be supposed to bi' adapted lor reliexing 

 the other arcolarconnections from the strain of the animars weight when 

 in an ai)pressed or vertical j)osition. Its nnifoiiiiity in the bnriowing 

 genera of the liufonida' an<l Scaphiopodida-, and especially on their dor- 

 sal surface, rather confirms this view. 



This connection is, however, evidently not necessary to the use of the 



*riatus 7-^ 73. 



