MORPHOLOGY OF THE COAL MEASURES AMPHIBIA. 35 



lowing description is based on Eryops megacephalus Cope from the Texas Permian. 

 The entire surface of the cranial elements in Eryops, as in other of the Stegocephala 

 (458), is covered with coarse pits. The fossae are present even in the bottoms of the 

 grooves which represent the lateral-line system, and are more marked in the mem- 

 bers of the Temnospondylia than in the Stereospondylia. 



The occipital cross-commissure occurs in a well-developed form in Eryops. It is 

 short and ends abruptly within the limits of the tabulare. Its ends are occupied 

 by large pits. The commissure, as in Amia, grooves the postparietal and the tabu- 

 lare elements. There is no evidence of an anterior commissure. I think there is 

 evidence of a temporal canal on the left side of the skull, but am not sure. The 

 jugal and infraorbital canals are well developed and strongly connected. The jugal 

 canal starts far back on the supratemporal, and after curving around over the quad- 

 ratojugal joins the infraorbital, or rather becomes a part of that canal, somewhere 

 on the jugal. There is nothing unusual in the infraorbital. The antorbital commis- 

 sure is well developed. It is longer and better developed than in any other known 

 form. The supraorbital canal starts in the region of the orbit, and after curving 

 downwards to meet the antorbital commissure, ends abruptly anterior to the nostril. 

 There are faint traces of a lateral-line canal, the operculo-mandibular, on a poorly 

 preserved mandible of Eryops. It does not differ greatly from that described below 

 for Anaschisma. 



Although Archegosaurus has been known for more than a century, we have had 

 no adequate discussion of the manner of occurrence of the lateral-line canals. Bur- 

 meister (80) gave a figure of the canals as he thought they occurred on the cranium, 

 but H. von Meyer (428) states that the representation is inaccurate, and they seem 

 to be based largely on Trematosaurus. 



The lateral-line canals occur in well-developed form on the skulls of the Stereo- 

 spondylia. The sutures between the elements of the skull are usually clearly marked 

 by smooth, narrow grooves. The lateral-line canals can always be distinguished 

 from the sutural grooves by the shape of the bottom, being U-shaped in the former 

 and V-shaped in the latter. The lateral-line canals also at times have their bottoms 

 roughened by pits occurring in them; the sutural grooves always have smooth bot- 

 toms. The lateral-line canals are usually rather shallow and sometimes broad, 

 with the edges of the grooves more or less perpendicular, but in Metoposaurus the 

 canals are deep and the borders are sharply incised. 



The temporal canals in Anaschisma from the Triassic (49) of Wyoming are rep- 

 resented by broken furrows. The portions preserved exhibit the usual downward 

 tendency to unite with the infraorbital on the postorbital element. In its course 

 forward from the epiotic the temporal canal cuts the squamosal. The supraorbital 

 canal has an unusually deviating course in Anaschisma, but aside from the minor 

 twists and curves it does not differ essentially from the same canal in other forms. 

 It ends abruptly on the anterior end of the muzzle. In its course it gives off the ves- 

 tige of an antorbital commissure which tends to join a vestige from the infraorbital 

 canal. The jugal canal begins broadly at the very posterior edge of the skull as 

 though it were continued, as it undoubtedly was, to the body of the animal. In its 



