MORPHOLOGY OF THE COAL MEASURES AMPHIBIA. 



33 



others are not so readily homologized. The upper canal (see fig. 6) in the posterior 

 part of the cranium is here designated the temporal canal. It is, however, clearly a 

 part of the infraorbital of the fishes. Its relations in the Stegocephala are 'such that 

 a new name is deemed necessary. The jugal canal is, I believe, a new formation in 

 Amphibia. The transverse canal of the amphibian skull is homologous with the 

 "occipital cross-commissure." 



The figure (see fig. 6) is a composite picture of the lateral-line system of the 

 higher or truly stegocephalous Amphibia. The outline of the skull is based on that 

 of Eryops. All of the canals do not exist on any one skull or in any one order, but 

 all are found somewhere in the group. 



FIG. ii. 



A. Skull of Eoserpeton lenuicorne Cope, showing arrangement of cranial elements. X 2. fr, frontal; 



j, jugal; mx, maxilla; n, nasal; or, orbit; par, parietal; pof, postf rental; pmx, premaxilla; po, post- 

 orbital; pp, postparietal; qj, quadratpjugal; sq, squamosal; spt, supraternporal ; tab, tabularc. 



B. Outline of skull of Ceraterpeton galvani Huxley from the Carboniferous of England. Heavy broken 



lines show the distribution of lateral- line canals. X I. (After Andrews.) fr, frontal; par, parietal; 

 or, orbit; po, postorbital ; pp, postparietal; spt, supratcmporal; tab, tabulari 1 . 



The canals have been described in all known orders of fossil Amphibia and the 

 system is found likewise in all the living orders, including the Gymnophiona, which 

 have "a strong line of lateral sense-organs" (Gadow). In the Branchiosauria, the 

 earliest of the true Amphibia (Euamphibia) and ancestral to the modern Caudata, 

 the lateral-line system is known on the tails of two genera (462, 478) from the Mazon 

 Creek, Illinois, shales Micrerpeton and Eumicrerpeton. The system as there 

 defined has been fully discussed in the description of the anatomical details of the 

 species, to which reference may be made for further data (pp. 52-60) . Suffice it to say 

 here that the system of sense-organs there preserved is identical with that of tlu- 

 larval Necturus; the lines arising as a median from the tip of the tail and a dorsal 

 springing from the median at a distance of a few millimeters from the tip of the tail. 

 The lines are more evident on account of the fact that the lateral-line sense-organs 

 were located under specialized pigmented scales. The significance of the close simi- 



