A IU SUN BIOa 
Metamorphosis after birth; respiration branchial in young, pulmonary 
or pulmonary and branchial in the adult, but always feeble in the 
lungs, while active from the skin; lungs with few and coarse cells; blood 
cold; corpuscles oval, nucleated; circulation incomplete; heart in adult 
with two auricles and a ventricley ; reproduction oviparous or ovovi- 
parous; foetus anamniate; allantois wanting, unless the urinary bladder 
represents itt; skin usually naked or unarmed; skeleton incomplete, 
internal; cranium with two occipital condyles; nasal sacs and pharynx 
connected; nervous system cerebrospinal; brain small; cerebellum 
scarcely visible; excrementitious and reproductive organs opening into 
a cloaca. 
The living forms are divided into three orders, as follows : 
Feet present, at least in front; body not vermiform. a. 
Feet wanting; body vermifcorm ; extralimital. . : j : OPIOMORPHA. 
a. Adult tailless; body short and thick. ANOURA. 
a. Tail always presezt; body lacertiloid. . 3 : : . . URODELA. 
ORDER ANOURA. TAILLESS AMPHIBIANS. 
Metamorphosis complete; young fish-like, herbivorous, with a long intestinal canal; 
gills external at first; teeth and limbs wanting ; adult without branchial arches; body 
short, depressed, raniform, tailless; feet four, posterior longer; tongue large, fleshy, 
free posteriorly, and capable cf protrusion; ear provided with an eustachian tube; fenestra 
rotunda presen{ ; nasal sacs and pharynx connected; hyoid bone with but one pair of 
coriua; radius and ulna anchylosed as are also the tibia and fibula; astragalus and cal- 
caneum replaced by two elongated, cylindrical bones; vertebra ten, without any dis- 
tinct atlas; ureters opening into the eviducis; fecundation after exclusion of tha eggs. 
* Por the anatomy of these animals, seo Brown’s Klassen und Ordnung des Thier- 
Reiches, and Duges’ Recherches sur l’Osteolegie ot la Myologie des Batraciens a leurs 
differens Ages. ; 
+ A question has been raisedin regard to the structure of the heart in the Perenni- 
branchiata, Proteus, and also the Axolotl in all probablity have only a single auricle. 
¢ Prof. Wyman, Proc. Boston Soc. Nat. Hist., p. 58, states from his observations that 
he considers the urinary bladder of frogs te structurally resemble that of fishes and 
scaly reptiles. From its anatomical relations to the intestine and vascular system he 
regards it as a rudimentary allantois. 
