252 



BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



The arid regions of the Southwest furnish the greater variety of species 

 of Bufo, but one species inhabiting tbe eastern region. The Austrori- 

 parian resiou is the home of several small forms of HylithTe and Bu 

 fonidse. Tlie distribution of the Scapliiopidfe is chiefly in the dryer 

 regions of the West; three species are found in tbe Sonoran, while but 

 one occurs in the Pacific, and one in the eastern and Austroriparian 

 regions. Tbe distribution may be tabulated as follows: 



Genera. 



Anstio- 

 ripariau R. 



Eastern. 



Central. 



Sonoran. 



Pacific. 



Bufo 



Seaphiopus. 

 Chorophiliis 



Hyla 



A oris. 



Hylodes 



Syrrhophus 

 Rana 



Totals 



AGL0S3A. 



The few members of this suborder liave the vertebrae opisthoccelous 

 and deprived of ribs ; the diapophyses of the third and fonrth vertebrte 

 are extremely elongate, and those of the sacral are strongly dilated and 

 confluent with the urost^ le. The third ceratobranchials are greatly 

 elongated. 



In Pipa there are only seven presacral vertebne. 



The frontoparietals are entirely ossified, and there arc true ossa 

 nasalia. 



The sternal apparatus belongs to the arciferous type, though the 

 epicoracoid cartilages do not overlap. 



ThelarvciB are provided with two spiracula, one on each side of the 

 body. (Boulenger). 



There are two recent and one extinct families of this suborder, which 

 are defined as follows: 



PIPID^. 



No ribs; vertebriie opisthoccelous; urostyle simple, attached to a 

 single condyle. Coracoid and epicoracoid divergent, their connecting 

 arches not overlapping. No manubrium. Teeth none; sacral dia- 

 pophyses dilated. 



The neotropical genus Pipa has the atlas confluent with the second 

 vertebra, so that there are but seven anterior to the sacrum. There are 

 distinct nasal bones, and the median septum of the ethmoid is partially 

 ossified. The prefrontals are completely in contact with each other and 

 with the frontoparietal. Frontoparietal completely ossified. Terminal 

 phalanges acute, simple. External metatarsals separated by a web. 

 (Plate 69, tigs. 1-2.) 



