222 GENEKAL EVOLUTION. 



EXPLANATION OF CUTS OF CRANIA OF ANURA. 



The numbers in each column correspond with the types of ossification mentioned 

 in the text, and are the same as those in the table of families given in the same con- 

 nection. The power numbers attached to Fig. 3, represent the degree of ossification 

 of the nasal bones, except the ~\ which signifies unossified ethmoid. Most of the 

 cuts are original. 



BcFONiDJE. — Fig. 2, anterior part of skull of Chdydohairachas gouldi Gray, from 

 Australia. Fig. 3, do. of Schismaderma carens Smith, S. Afi"ica. Fig. 6, top 

 of head of Peltaphryne peltacephala D. and B., Cuba. Fig. 7, top of head of 

 Otaspis empusa Cope, Cuba. 



SoAPHiopiD^ AND Pelobatid^. — Fig. 2, diagram of top of cranium of Didocus 

 ccdcaratus Micahelles, Spain. Fig. 5, skull of Scaphiopm liolhroolci Harl., 

 United States. Fig. 6, skull of Cultripes provincialis, from France, after 

 Duges. 



llYLiDiE. — Fig. 1, Thoropa miliaris Spix., Brazil. Fig. 2, Hupsiboas doumerci D. 

 and B., Surinam. Fig. 2\ Hypaihoas punctatus Schn., Brazil. Fig. 3^, Scytopis 

 vemdosus Daudin, Brazil. Fig. 6, Trachycephalus geographicus D. and B., 

 Brazil, after Steindachner. 



Cystignathid^. — Fig. 1, Eusophus nehuloaiis Gir., Chili. Fig. 2, Borhoroccetes tas- 

 maniensis Gthr., Tasmania. Fig. 3, Elosia nasiis Licht., Brazil. Fig. 3^, Ify- 

 lodes oxyrhyiichus D. and B., W. Indies. Fig. 4, Grypiscus umbrinus Cope, 

 Brazil. Fig. 6, Calyptocephalus gayi D. and B., Chili. 



Ranid^. — Fig. 3~^ — Ranula chry&oprasina Cope, Costa Rica. Fig. 3, Rana oxy- 

 rhyncha Sund., S. Africa. Fig. 3\ Rana clamata Daud., N. America. Fig. 3^, 

 Rana agilis Thomas. Fig. 3'^, Rana hexadactyla Less., India. Fig. 4, PoJy- 

 pedates quadrilineatus D. and B., Ceylon. 



to geologic time are displayed in the follo^^ng table, commencing 

 with the lowest horizon : 



No cannon bono. Cannon bone present. 



Incisor teeth present. Incisors one and two wanting 





4 premolars, 3 prem'rs. 2 prem's. 1 prem'r. 



r- 



Lower Miocene. -] Pochrotherium. 



{ Protolahis. 



Upper Miocene. < Procamelus 



Pliocene and Recent. 



( Pliauchenia. 



Camelus. 



Auchenia. 



This table shows that geological time has witnessed, in the his- 

 tory of the CamelidcB, the consolidation of the bones of the feet 

 and a great reduction in the numbers of the incisor and premolar 

 teeth. The embryonic history of these parts is as follows : In the 



