11 



The foetus has no embryonic sac (amnion) and the allantois 

 (organ by which foetal blood is aerated in the higher animals) 

 is absent. 3 



The skeleton is internal. The vertebrae of our frogs and 

 toads are procoelous (concave in front only). There are nine 

 of these and a peculiar bone, the urostyle, which articulates 

 with the sacrum. The skull articulates with the first vertebra 

 or atlas by two occipital condyles, and the nasal sacs open pos- 

 teriorly into the pharynx. The reproductive, urinary and 

 digestive organs open into a common receptacle, the cloaca. 



Our Salientia are divided into two sub-orders, the Arcifera 

 (toads and tree-frogs), in which the opposite halves of the 

 scapular arch are connected by an overlapping arched cartilage 

 (the shoulder girdle), so that the thorax may contract or ex- 

 pand ; and the Firmisternia (frogs), in which the opposite 

 halves are connected by a single median cartilage and are 

 incapable of movement. In the tadpoles of the latter division 

 the shoulder girdle is movable (arciferous), but becomes con- 

 solidated upon maturity. 



The family divisions are based principally upon the presence 

 or absence of teeth and their arrangement and the shape of the 

 sacral diapophyses, and present many parallel modifications of 

 structure. 



The genera exhibit differences in the bones and webs of the 

 feet and the ossification of the bones of the cranium. 



Specific differences will be found under their respective 

 headings. 



The known North American frogs and toads are embraced 

 in twelve genera and fifty species, of which five genera and 

 eleven species are found in this vicinity. Some of these are 



lungless species, all agreeing closely with this description. Up to the 

 time of his paper seventeen species had been described as without lungs, 

 and he had found an additional one, Spelerpes guttolineatus. 

 Of our local forms, those thus described were : 



Amblystoma opacicm, Spelerpes bilineata, 



Plethodon cinereus, Spelerpes ruber ; 



Plethodon erythronotus ; Desmognathusfusca. 

 Ptethodon glutinosus, 



3 An explanation of the means of nourishment of the fcetus will be 

 found in Note 2, page 13. 



