124 



BULLETIN 34, UNITED STATES NATIONAL MUSEUM. 



animal is still braiichiferous and possesses the larval tougne, etc. The 

 same ocLirs in Spelerpes when certain of its species present bat four 

 hind toes, as in Manculus; therefore the relation of these two is also of 

 inexact parallelism. The relation of Thorins is also one o? inexact par- 

 allelism, for though its characters are found in some young Spelerpes at 

 an immatjire age subsequent to the absorption of the branchiae, it has 

 opisthoca'lns vertebrae. With CEdipus, if the condition be not that of 

 exact parallelism with some species of Spelerpes, the approach to it is 

 close, as above observed. It is chiefly prevented by the fact that the 

 ossification of the parietal bones in most species of the latter takes 

 phice after the extremities are fully developed. It is to be observed in 

 tliis connection that, as has been above pointed out, the separation of 

 the digits takes place at very different periods in the history of the differ- 

 entspecies of the same genus. Thus in the Spelerpes ruber they are en- 

 tirely distinct at a very early period of larval life, while in S. cepkalicus 

 and 8. bellii, which much more nearly resemble the species of (Edipus 

 in the disposition of the vomerine teeth and cylindric form of the tail, 

 this separation is much retarded. 



Tiiese genera may be parallelized also in the following manner in 

 illustration of the law of heterology : * 



PLETHOUONTiE. 



Stereochilus. 



Autodax. 



Bafraclwseps. 



Heniidactjjliiim, 



A. One premaxillary. 

 No foutauelle. 



A foutanelle. 

 Toes 4-5. 

 Teeth large. 



Teetli amall. 



Toes 4-4. 



AA. Two premasillaries. 

 Toes free. 



Spelerpes. 



Spelerpes. 

 Manculus. 



Flethodon. 



Toes united. 



GijrinopMlus, 

 Geotriton. 



The miuor relations 



may be more readily expressed th 



as: 



Pi.ETHODONTJE. 



Digits 4-5. 

 a. Digits distinct. 



Spelerpes. 



Flethodon. 



Two premasillaries. 



GyrinopMhis. 



Autodax. 



One premaxillary. 

 a. Digits united. 



Spelerpes. 





Two premaxillaries. 



Geotriton. 



Remidacti/lium. 

 Batrachoseps. 



One xiremaxillary. 

 Digits 4-4. 



(Edipus. 

 Manculus. 



See Origin of Genera, !>. o3. 



