I 



THE BATRACHIA OF NORTH AMERICA. 13 



CLASSIFICATION. 



There are several orders of Jiatrachia, and they disi)lay remarkable 

 diversities of skeletal structure. For the better understaudiug of these 

 I give the following table of their principal definitions:' 



I. Basioccipital, supraoccipital, iutercalaiy,- and supratemporal lioues present. Pro- 



poilial boues rlistiuct. 

 a. One cotyloid occipit.al condyle, 



Vertebral centra reidaced by one basal and two lateral elements 



witli one nenral arcli GimoceiihaUi. 



aa. Two occipital condyles. 



Vertebral Viodies, including atlas, segmented, one set of segments 



togt*lier suppcrting one arch L'hachitomi. 



Vcrtebr.T segni< nted, the superior and inferior segments each 



complete, forniini; two centra to each arch Emholumeri. 



Vertebral bodies, including atlas, not segmented: one to each 

 arch Sttgocephdli. 



II. Basioccipital, suiiraocciiiital, and supratempi>"al bones wanting. Frontal and 



propodial bones distinct. 

 a. Au OS intercalare. 



A palatine arch and separate caudal vertebra? Prottida. 



aa. No OS intercalare. 



A maxillary arch and vomers; palatine arch present, imperfect; 



nasals, iiremaxillaries and caudal vertebne distinct Vrodtla, 



No niBxillary or palatine arches; no vomers: .lasals and pre- 



maxillary. also caudal vertebra*, distinct. Trachi/'stumata. 



III. Basioccipital, su])raocci))ital, intercalare. and supratemjioral boues wanting- 



Frontals and ]>arietals connate: proi)odial bones and lumbosacral vertebra^ 

 each continent. 

 Palatines distinct from vomers; a palatine arch : a.stragalus and 

 calcaneum eloiiy,ate, forminu a distinct segment of the limb Salientia. 



The animals of the liivision I are all extinct. Division II includes the 

 Salamanders and their allies, witii the worm-like C<ecilians (Aj>oda), 

 while the third division embraces the frogs, toads, etc. 



AFFINITIES. 



The Batrachia are, tlien, intermediate in characters, and therefore iu 

 position, between the tish-like forms and the reptiles. Among the 

 former the Dipnoi ai)pi'oacii tliem most nearly, while the extinct reptiles 

 of the oldest order, the Theromora,^ are the nearest allies on the rep- 

 tilian side. It belongs to the series of vertebrates which have a dis- 

 tinct coracoid bone in tiie shoulder-girdle, ami a distinct quadrate bone 

 in the skull. The greater part of the basicranial axis is cartilaginous, 

 but it is protected below by the membrane bone, the parasplienoid. In 

 all these respects, and in the absence of an amnion of the embryo, the 

 Batrachia agree with the fishes. They differ from tiiischissin the jtres- 

 ence of legs and absence of fins, and in the absence of various bones 

 whi(!h belong to the l)rauchial and opercular .systems, and to tin- sus- 

 ])en,sor of the lower Jaw. 



'This is partly derived from the talde which I have given iu Vol, if. Paheontology 

 of the Geological Survey of Ohio, l-iTI, p. ;!,";). See also Americau Naturalist, 1-84. 

 'Of Cnvier : Kpiotic of Iluxloy, according to Vrolik. 

 ^ Thcromor2)ha Cope olim; name preoccupied. 



