32 THE COAL MEASURES AMPHIBIA OF NORTH AMERICA. 



Among the Paleozoic Amphibia from Nova Scotia as described by Dawson and 

 Owen (193, 201, 485) scales are well developed and frequent, although the details 

 as to their occurrence on the bodies of the animals are still unknown, since the Nova 

 Scotian species are all based on very fragmentary remains. Dawson (208, p. 34) 

 has given a detailed discussion of the discovery and anatomy of the various types 

 of scales possessed by the species from the Coal Measures of Nova Scotia. Suffice 

 it to say here that none of the scales appear to be bony, but have a cuticular appear- 

 ance with concentric markings. Some of them are tubercular, and Dawson thought 

 that a few specimens indicated that some of the species possessed scaly lappets and 

 a dorsal nuchal fringe of scaly skin along the back. He has indicated these facts 

 in his restorations of the forms. The scales were all carbonized and burned readily 

 with a strong flame. A section of the scale shows a thick upper corium with a vas- 

 cular body (208, pi. IV, fig. 29) much like a fish-scale. Fragments of the skin were 

 also preserved with the scales. Dawson says of the skin: 



"One of my specimens is a flattened portion of cuticle two and a quarter inches in 

 length. The greater part of the surface is smooth and shining to the naked eye, and under 

 the microscope shows only a minute granulation. A limited portion of the upper and, I 

 suppose, anterior part is covered with imbricated scales, which must have been membra- 

 nous or homy, and generally have a small spot or pore near the outer margin, some having 

 in addition smaller scales or points on their surfaces" (208, pi. iv, figs. 22 and 25). 



(t) Muscle tissue (fig. 21) is preserved in a single specimen, previously described 

 by the writer (464, p. 17, pi. 7, fig. i). The carbonized muscles show a myomeric 

 arrangement and the portions preserved probably represent one of the recti muscles 

 of the abdominal wall. 



(u) The lateral-line system in the Coal Measures Amphibia will be best tmder- 

 stood from a comparative review of the occurrence of these organs among all extinct 

 Amphibia. Since all the orders of Amphibia are represented in the Coal Measures, 

 such a review will not be out of place here. 



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 Macropetalichthyidae, 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. 11, pt.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 (Joum. of Morphology, vol. 11, 1889). The supraorbital and infra- 

 orbital 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 



