ON TEE ORIGIN OF GEKERA. 



101 



Insedivora. 



Gymnura. 

 Cladobates. 



a. Tubercular molars |, toes 4 — 5. 

 Tail naked. 



Tail hairy. 



Entomophaga. 



Didelpbys. 

 Myoietis 



rV. Molars with transverse crests, no canines ; tusk-like incisors ; pairs of limbs of 

 similar proportions. 



Froboscidia. Diprotodontidfe. 



Two inferior incisors ; molars with two cross-crests ; size huge. 

 a. Two rudimental lateral incisors above. 



* * Diprotodon. 



aa. ? One pair of incisors only above ; a trunk. 

 Dinotherium. 



Y. No canines ; two pairs of cutting incisors. 



«. Three true molars. 

 Rodentia. * * 



aa. Four true molars. 



* * Rkizophaga. 



The parallels are in this case very imperfect in details, and but 

 few worthy of the name can be made. They are, however, illus- 

 trative of a remote heterology, sufficiently remarkable to have 

 claimed the notice of naturalists for many years. "^ I also have 

 little doubt but that future paleontological discoveries will in- 

 crease the number of parallels, f and bring to light truly heterolo- 

 gous generic terms of the Marsupial series. Predictions of this 

 kind have been on many occasions fulfilled (e. g., some of D'Or- 

 bigny's among the Cephalopoda), and I look with confidence to 

 the ultimate demonstration of that heterology here which has 

 been already seen in the Batrachia and Reptilia. 



The homologous groups of the Catarrhine and Platyrrhine 

 Quadrumana are measured as follows : 



* We owe very many observations on the Marsupials to Owen. 



f The extinct carnivorous family of the Nimravidae which forms a homologous 

 series with the cats (Felidae) was discovered by the writer some years after this was 

 written. (Ed. 1886.) 



