THE BATRACHIA OF NORTH AMERICA. 



BATRACHIA. 



Bongniart, 1800, Amphibia Latreille, 1825 (not of Linnseus 1766). 

 GENERAL CHARACTERS. 



Vertebrata with a distinct coracoid element of the scapular arch and 

 with an os quadratum. The limbs consist of a single proximal element, 

 two propodials (sometimes united), a carpus and tarsus, metapodials, 

 and phalanges. The cartilage of the basis-cranii unossified (except some- 

 times a basioccipital ossification), but supported by the single mem- 

 brane bone, the parasphenoid ; vertebral column consisting entirely or 

 in part of intercentra. Stapes present. 



Brain with the cerebellum small, and the mesencephalon smaller than 

 the prosencephalon ("hemispheres"); the latter with the ventricles on 

 the inner side of their principal mass. 



Heart with three chambers, two auricles, and a ventricle. Three or 

 four aorta bows on each side. Lungs always present. 



Gall-bladder and urinary bladder present ; oviducts entirely distinct, 

 and opening by fontanelles into the abdominal cavity at a distance from 

 the ovaries. Eeproductive, renal, and digestive products discharged 

 into a cloaca. Male without distinct intromittent organ. 



In development the embrj'onic life is prolonged during a period of 

 freedom subsequent to leaving the egg, constituting a larval stage. 

 During this period the young is branchiferous and generally aquatic in 

 its habits, i^o amnion nor allantois. Segmentation of the yolk complete 

 or holoblastic. 



GENERAL ANATOMY. 



The auditory organs resemble those of other terrestrial vertebrata, 

 and differ from those of fishes, in the presence of a fenestra ovalis of 

 the internal ear, which is closed by a stapes. The other ear bones or 

 their equivalents are fused at an early stage of growth with the sus- 

 pensorial cartilage of the lower jaw (Parker). There are three semi- 

 circular canals, but the helix is represented only by a diverticulum of 

 the sacculus. 



The hyoid apparatus is less complicated than that of the JMsces, and 

 more so than that of the vertebrate classes above them in the series. 



