222 GENERAL 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. 



BuFONiD-E. — Fig. 2, anterior part of skull of Chelydohairachus gouldi Gray, from 

 Australia. Fig. 3, do. of Schismaderma careris Smith, S. Africa. Fig. 6, top 

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

 Oiaspis empusa Cope, Cuba. 



SdAPHioPiDJE AND Pelobatid.?;. — Fig. 2, diagram of top of cranium of Didocus 

 calcaratus Micahelles, Spain. Fig. 5, skull of Seaphiopus holbrooki Harl., 

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

 Dugfes. 



IIyud^. — Fig. 1, Thoropa miliaris Spix., Brazil. Fig. 2, II>/psihoas doumerci D. 

 and B., Surinam. Fig. 2', Hypsiboas pundatus Schn., Brazil. Fig. 3^, i^cytopis 

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

 Brazil, after Steindachner. 



Cystignathid^. — Fig. 1, Eusoplms nebidoxus Gir., Chili. Fig. 2, Borboroccetcs fas- 

 maniensis Gthr., Tasmania. Fig. 3, Elosia nasits Licht., Brazil. Fig. 3^, Jly- 

 lodcs oxyrhynchus D. and B., W. Indies. Fig. 4, Grypiscus umbrinus Cope, 

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



Ranid^. — Fig. 3~^ — Ranula chrysoprasina Cope, Costa Rica. Fig. 3, Jiana oxy- 

 rhyncha Sund., S. Africa. Fig. 3', Rana clamata Baud., N. America. Fig. 8^, 

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

 pedates quadrilincaius D. and B., Ceylon. 



to geologic time are displayed in the following 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. 



^_ 



Lower Miocene. ■] Poebrotherium. 



iProtoIabis. 

 Procamelus. 

 Pliauchenia. 



Pliocene and Recent. \ ' a i ■ 



I 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 



