Si ON THE STRUCTURES AND DISTRIBUTION OF THE 



strain of the animal's weight when in an appressed or vertical position. Its uniform- 

 ity in the burrowing genera of the Bufonidse and ScaphiopodidaB, and especially on 

 their dorsal surface, rather confirms this view. 



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

 integument as an adhesive supjDort, as this faculty is nowhere better seen than in 

 Acris, where the derm is free. This creature will adhere for days to a vertical glass 

 plate, not only by the abdomen and digits, but by the interdigital membranes, and 

 will light securely from a long leap on such a surface. Daudin and Dumeril have 

 related the same adhesive faculty in Pelodytes p u n c t a t u s, which is not known in 

 regard to the dermal attachments, but has not the abdominal areolte present in Acris. 

 The extent of the attachment is least where the dilatations are smallest, as follows : 



Abdomen entirely attached ; 18 sp. 

 Phyllomedusa two sp. Pithecopus two sp. Agalychnis three sp. Trachycephalus 



two sp. Nototrema one sp. Scytopis two sp. Smilisca baudinii. 

 Hyla albomarginata, boans, agrestis, krefftii, phyllochroa. 



Posterior half or third of abdomen attached ; latero- ventral band wide. 

 Triprion petasatus. 



Hyla fusca, arenicolor,* gratiosa, versicolor, femoralis ; squirella, andersonii, cyanea. 

 Ranoidea aurea. 

 Chorophjlus triseriatus. 



Less than posterior third abdomen attached ; the latero-ventrals wide. 

 Hyla arborea, regilla, lateralis, cadaverinaf miotympanum ; pickeringii. 

 Chorophilus nigritus. 



Abdomen entirely free. 

 Hyla leseurei, curta, gracilipes. Acris gryllus. 



Of distinguishing features, which refer to the conditions of the elements of the 

 vertebrate skeleton, their degree of developement, etc., it may be said that they 

 exhibit far fewer cases of questionable or intermediate existence than those of the 

 previous class. They are, first, the developement of the o. o. frontoparietalia ; 

 second, of the prefrontalia ; third, of the superficial cranial rugosities ; fourth, of 

 vomerine teeth ; fifth, of a postfrontal arch ; sixth, of the ethmoid arch. 



Whole number of species, . . . . . . . . . .131 



Frontoparietals fully developed, . . . . . . . .19 



" with rugosities penetrating derm,. . . . . .11 



Prefrontals developed, . . . . . . . . . . .17 



* H. affinis Baird, not Spix. 



t H. nebulosa Hallow., not of Spis. 



