No. 2.] LATERAL, LINE IN EXTINCT AMPHIBIA. 535 
ein Theil des Hauptastes, namlich der, welcher bei andern 
Fischen dem Squamosum zukoniunt, durch das Parietale geht, 
dass dieser Knochen auch an der Begrenzung der Gelenk- 
pfanne fur das Hyomandibulare theilnimmt, was bei andern 
Fischen ebenfalls das Squamosum thut, und endlich dass das 
Schadeldach keinen besonderen Knochen besitzt, der auf den 
Namen Squamosum Anspruch erheben kann, so ist es kaum 
zu bezweifeln, dass der bis jetzt als Parietale bei Polypterus 
beschriebene Knochen ein Squamoso-parietale ist,’ the so- 
called parietal is the squamoso-parietal. He is followed in 
this by Pollard. 
I do not find that the arrangement of the canals on the 
skull of Polypterus has ever been given in an accurate dia- 
gram. Tranquair gives a verbal description of their course 
(24). Van Wijhe remarks: “Thren Verlauf (i. e. die Schleim- 
kanale in Polypterus) habe ich nicht verfolgt, er ist aber von 
Traquair beschrieben” (25). Pollard’s representation is 
modified after Wiedersheim and Bautr’s figure is modified after 
Pollard. According to Traquair’s description of the course 
of the canals, all of these figures are inaccurate in regard to 
the course of the main canal. Traquair says the infraorbital 
gives off the supraorbital canal on the postfrontal and I have 
represented it thus in the diagram (Fig. 3). In Polypterus 
according to Traquair the main canal is the infraorbital as 
it is in the Stegocephala. 
The course taken by the lateral line canals is not subject 
to great change. This is suggested by the condition described 
for Micrerpeton and Necturus. If the temporal canal, whicn 
is the posterior part of the infraorbital canal, cuts a certain 
element in one form and cuts the same element with the 
same relations in another and related form, it is safe to as- 
sume that the element is identical in the two forms. We have 
thus a definite basis for conclusions regarding the homolo- 
gies of the cranial elements in the two groups; fishes and 
stegocephalans. It is easy to understand the correlations 
of the premaxillaries, maxillaries, nasals, frontals, prefontals 
and parietals of the fishes with the same elements in the 
