No. 2.] LATERAL LINE IN EXTINCT AMPHIBIA. 529 
individual variation since it is very slight. But it is the lateral 
line canals that the chief points of resemblance lie. The gen- 
eral plan of the canals is identical in the two skulls. The only 
difference is this: the connection between the temporal and 
supraorbital canals is absent in the younger skull while in the 
adult it is well developed. The pits in the bottoms of the 
Fic. 13.—The skull of Metoposaurus diagnosticus von Meyer, showing 
the manner of distribution and occurrence of the canals. After Fraas. 
One-fifth natural size. 
canals are more clearly marked in the younger than in the 
adult skull, and this is an indication of youth. There is 
another factor which tends to corroborate the statement as to 
the specific identity of the two skulls. They were found to be 
slightly overlapping each other in the rocks. This might 
