No. 2.] LATERAL LINE IN EXTINCT AMPHIBIA. 521 
The infraorbital, the anterior commissure, and the jugal canals 
were not detected. The presence of a well-developed occipital 
cross-commissure in the skull of Ceraterpeton is of interest 
because this structure is rarely present in the more highly 
specialized labyrinthodonts. This is a generalized character 
as may be seen by referring to the figures of the Actinoptery- 
gian, Amia, and the Crossopterygian, Polypterus, in both of 
which the occipital cross-commissure is well-developed. The 
Fic. 7.—Outline of the skull of Ceraterpeton galvani Huxley from the 
Carboniferous of England, showing the distribution of the lateral line 
canals. After Andrews. Natural size. 
Fic. 8.—Outline of the skull of Tuditanus tabulatus Cope, showing the 
arrangement of the lateral line canals in their relations to the cranial 
elements. One and one-third natural size. 
Fic. 9 —The mandible of Diplocaulus magnicornis Cope, showing oper- 
culo-mandibular canal from the side. One-half natural size. 
temporal canal, which is a portion of the infraorbital, begins 
its course on the epiotic and crosses most of the squamosal 
when it is lost. The supraorbital canal occurs on the frontal 
and postfrontal and has the usual relations for that canal. 
The lateral line canals are but weakly developed in the - 
cranial region of Diplocaulus. On a nearly perfect skull and 
mandibles of the species D. magnicornis Cope in the collection 
of the University of Chicago, there are traces of only three of 
