GENERAL CHARACTERS 165 



The only known specimens were obtained in the water from an 

 artesian well near San Marcos in Texas. 



II. ANURA, TAILLESS AMPHIBIANS OR BATRACHIA SALENTIA. 



This is the largest Order of existing Amphibia, containing 

 about 900 species, and the differences between them are some- 

 what slight. They are divided into three sub-orders: (1) the 

 Aglossa, in which the tongue is absent ; (2) the Arcifera, in 

 which the two halves of the pectoral girdle are not united to- 

 gether but overlap one another ; (3) Firmisternia, in which the 

 halves of the pectoral girdle are united together by cartilage. 

 These two divisions of Batrachians with well-developed tongues 

 are typified by the toad and the frog. The Hylidae, usually 

 called tree-frogs, are really allied to the toad. 



Sub-Order Firmisternia. 



This sub-order contains only two families, the Ranidas 

 or common frogs, and the Engystomatidae or narrow-mouthed 

 frogs. 



Fam. RANID/E. — Rana temporaria is the common English 

 frog, which is equally common on the continent ; it is also called 

 the brown frog or grass frog. The male has two vocal sacs of the 

 kind called internal, that is to say they are entirely covered by 

 the skin which is simply distended by them when they are in- 

 flated. The male has also a swollen pad of skin on the inner 

 side of the first finger which becomes enlarged and black in the 

 breeding season. The habits are distinctly terrestrial, the 

 animals only seeking the water in order to breed. Rana escu- 

 lenta, the edible frog of the continent, reaches a larger size and 

 is distinguished by the following characters : the toes are webbed 

 to their extremities, the vocal sacs are external and there is a 

 prominent glandular patch of skin behind the eye. The habits 

 of this species are much more aquatic than those of R. tempo- 

 raria, and it is never found far from water, into which it always 

 retreats when alarmed. This species is not a native of the 

 British Isles, but it was formerly found in Cambridgeshire and 

 is now abundant in some parts of Norfolk. Specimens are 

 known to have been imported from France and Belgium and 

 turned loose in recent years, and they were probably imported 



