No. 2.] LATERAL LINE IN EXTINCT AMPHIBIA. 531 
Whether or not the canal completed the course around the 
mandibles is not to be determined from the specimens at hand. 
The close resemblance between the arrangement of the 
lateral line canals of Metoposaurus (18), and that already 
described for Anaschisma is made evident by a glance at the 
figures (Figs. 12,15). This is indicative of the affinity which 
the osteology of the two genera exhibits. The forms are, 
however, generically distinct as Branson has pointed out, by 
the absence of the characteristic ear slit in the latter genus. 
The arrangement of the lateral line canals would separate the 
forms generically if other characters were lacking. Since 
the canals have such a similar arrangement in the two forms 
only the differences need be pointed out and the detailed 
description given for Anaschisma will serve for Metopo- 
saurus. ‘There are no traces of an occipital cross-commissure 
in either form, nor indeed have I been able to detect traces of 
this canal in but one of the stereospondylous forms. The main 
difference between the two forms lies in the absence of con- 
nection between the temporal and supraorbital canals (Fig. 
i5), and in the more direct course of the latter canal in 
Metoposaurus. Other characters are almost identical in 
the two groups. The skull of Metoposaurus shows its spe- 
cialized characters in the smoothness of the bottoms of the 
canals in the anterior part of the skull, and in the canals all 
over the skull, being more sharply defined than they are in 
Anaschisma. 
The skull of Mastodonsaurus giganteus Jeger, fragments 
of which were first discovered by Dr. Jeger, in 1824, is the 
largest and first known of all of the extinct Amphibia. The 
skull reaches, at times, enormous proportions for an amphi- 
bian, often attaining a length of four feet with a posterior 
breadth of two and one-half feet. The lateral line canals are 
clearly marked on all of the skulls known or at least on all 
which have been figured (Fig. 16). There are no evidences 
of the occipital cross-commissure in an excellent photograph, 
published by Fraas (18, PI.I), nor does that author indicate 
such a canal in the figure (18, p. 44), he gave of which the 
