No.2] LATERAL LINE IN EXTINCT AMPHIBIA. 525 
which represent the lateral line system. This character is 
more marked in Eryops than in the Stereospondylia, a matter 
of considerable importance as we shall see. 
The occipital cross-commissure is well-developed in Eryops. 
It is short and ends abruptly within the limits of the epiotics. 
Its ends are occupied by large pits. The cross-commissure, as 
in Amia, grooves the supraoccipital and epiotic elements. 
There is no evidence of an anterior commissure. I think there 
is an evidence of a temporal canal on the left side of the skull, 
but am not sure. This part.of the skull is imperfect on the 
right side. The jugal and infraorbital canals are well-developed 
and strongly connected. The jugal canal starts far back on 
the supratemporal (prs), and after curving around over the 
quadratojugal joins the infraorbital somewhere on the jugal. 
There is nothing unusual in the characters of the infraorbital. 
The antorbital commissure is well developed in Eryops. It 
is longer and better developed in this form than in any other 
known to the writer. The supraorbital canal starts anterior 
to the nostril and makes a decided bend downwards to meet 
the antorbital commissure. It ends abruptly on the postfrontal 
bone. The squamosal is apparently not grooved in this form. 
The position of this element is a little doubtful as Branson has 
stated and the diagram of the cranial elements given is based 
on his studies of the skull. The antorbital commissure is 
primitively a branch of the supraorbital. It is such in the 
fishes and Dr. Takahashi informs me it is the same in Nec- 
turus. It would be an interesting matter if we could deter- 
mine the points of origin of the lateral line canals in Eryops, 
and some day this may be known when we get material rep- 
resenting the youthful stages of the form. The peculiarly 
specialized condition of the lateral line canals bears witness 
to the specialization of the form. This is borne out by its 
osteology. Branson has shown that in its vertebral struc- 
ture it is approaching the Stereospondylia, the most highly 
specialized of all of the Stegocephala. 
There are faint traces of the lateral line canals on a poorly 
preserved mandible of Eryops in the collection of the Univer- 
