The preservation of the lateral-line system among ancient Amphibia is due to the fact that the skull of many forms (especially the later and larger) are grooved and marked by a regular series of furrows and pits, in which the sense-organs of the lateral-line system were contained (see fig. 6), as well as by the preservation of a series of clearly marked scales on the sides of the tails and bodies of others. The grooves are never arched over as in the Macropetalichthyidæ, where "in favorable specimens each is shown to be covered by a delicate roof perforated by two lines of minute openings" (Dean, N. Y. Acad. Sci. Mem., vol. II, pl. III, p. 115). They are always widely opened canals, either with perfectly smooth bottoms and sides or roughened with large pits, or even becoming a series of well-marked pits. An attempt has been made (458) to homologize the organs with those of fishes. The nomenclature adopted here for the canals does not depart from that used by Allis for _Amia_ (Journ. of Morphology, vol. II, 1889). The supraorbital and infraorbital canals are readily correlated with those of the same name in fishes, where they are very clearly marked. The anterior commissure is also homologous with that of the fishes, as is also the canal here called the "antorbital commissure." The 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. [Illustration: Fig. 11. A. Skull of _Eoserpeton tenuicorne_ Cope, showing arrangement of cranial elements. × 2. _fr_, frontal; _j_, jugal; _mx_, maxilla; _n_, nasal; _or_, orbit; _par_, parietal; _pof_, postfrontal; _pmx_, premaxilla; _po_, postorbital; _pp_, postparietal; _qj_, quadratojugal; _sq_, squamosal; _spt_, supratemporal; _tab_, tabulare. B. Outline of skull of _Ceraterpeton galvani_ Huxley from the Carboniferous of England. Heavy broken lines show the distribution of lateral-line canals. × 1. (After Andrews.) _fr_, frontal; _par_, parietal; _or_, orbit; _po_, postorbital; _pp_, postparietal; _spt_, supratemporal; _tab_, tabulare. ]