126 



THE GEOLOGIST. 



identifying the lower jaws with the forms to which they belong. No 

 specific dissimilarity in size or position of the teeth meeting each 

 other has been noticed by me. None of the limb-bones can be iden- 

 tified to belong to the same individuals as the crania or lower jaws. 



I give the characters of the genus from Gervais, and the synonyms 

 according to my own views : — 



Caii^otheritjm, JBravard. 

 " Teeth in continuous series ; certainly molars [= premolars 

 molars four toes, of which the two median digits are the 



largest, and similar to each other; the two last very slender." — Ger- 

 vais, loc. cit. 



1. Caifotheeitjm commutte, Brav. memoir on Cainotlievium — 

 following species : — C. laticiirvatiim, Pomel, loc. cit. C. elegans, 

 Pomel, I. c. G. gracile^ Pomel, I. c. C. leptorlnjnclium, Pomel, 

 ' Bulletin de la Societe Geologique de Prance,' 1846, t. iii. p. 369. 

 O. medium^ Brav., I. c. C. minimum, Brav., I. c. * ^ Hyccgulus col- 

 lotarstis, Pomel, I.e. * ? HycBgulus murinus, Pomel, I. c. = C. Cour- 

 toisii, Gervais. Oplotlieriim laticurvatum, Laizet and De Parieu. 

 Oplotherium leptognatliim, Laizet and De Parieu. MicrotJierium 

 Menggeri, H. v. Meyer. MicrotJierium concinnum, H. v. ISIeyer. 

 Cainotlieriiim majus, Pomel, MS. ? CaiiiGtherium lepthelicium, 

 Bravard, MS. ? 



2. Caixothertum metopium, Pomel, I. c. A veiy doubtful species. 

 In British Museum ? 



The problem of specific creation and extinction can be best Avorlved 

 out upon such genera as Cainothcriiim. Speculation miglit lead a 

 Natural-Selectionist to imagine how the four-toed Cainotlieria of the 

 Miocene, by reason of their firmer footing in a muddy soil, might have 

 been able to go deeper in a river in quest of food, and have supplanted 

 and caused the extinction of the Dichohunes of the Eocene, who had 

 only one small digit at the back of their foot, making three toes in all. 

 The difierences between, e.g. Cainotlierium^ Diclioliine, Xipliodon, and 

 Dichodon, and ApJielotJierium, are such as we might suppose might be 

 altered through the lapse of long generations. Whether such altera- 

 tion was slow and gradual by Natural Selection or any similar process, 

 or whether it was not rather due to a more rapid and sudden method 

 of operation, is the problem which the latter half of the nineteenth 

 century may perlmps solve by experiment, observation, or logical de- 

 monstration. In tlie meanwhile, to those who bear in mind the Lin- 

 iia^an maxim, Onmis vera eognitio cognitione specijica inj2itatur,f the 

 study of the minute differences of tlie Cainotlieria affords an instruc- 

 tive topic. 



* T liavciiot scon any autlicnlic specimens of these species. The C. Couiioisii 

 Gervais appears not lo he <\)Vi'\iu-,\]\\ distinct from some specimens of C. commune 

 t Linnc, ' Spt-i i. s 11;iiii:inini," S\o, Vindobouse, 176i, p. 3. 



