l68 AMPHIBIA AND PISCES OF THE PERMIAN OF NORTH AMERICA 



Referred specimens: 



1. A right mandibular element, the type of Gnaihorhiza serrata. No. 



7258 Am. Mus. Cope Collection. Texas. 



2. A left mandibular collected by Case in Texas, larger and better 



preserved than either of the preceding. No. 7935 Am. Mus. 



Description of species: Dental plates relatively small, with oral face 

 adapted for cutting or chopping rather than grinding. Inner oral margin 

 compressed into a sharp edge angulated near its middle and with one or two 

 sharp ridges radiating from the angulation; anterior moiety of coronal ridge 

 with two or three broad denticulations; posterior moiety, as well as radiating 

 ridges, finely serrated. 



CROSSOPTERYGII. 



Genus MEGALICHTHYS Agassiz. 

 Poiss. Fos., II, pt. II, 1844, pp. 89, 154. 

 A Crossopterygian genus belonging to the family Osteolepidce. 



Revised description of genus: 



1. Cranial bones arranged as in typical Osteolepida, with paired frontals 



and parietals. 



2. Throat region protected by a pair of large gular plates, an anterior 



median gular plate, and a series of small lateral plates. 



3. Teeth conical, those in front part of jaw much larger than the others. 



4. Vertebrae ossified in the form of rings, with well-developed neural 



and hsemal arches. 



5. Paired fins covered with scales except in their distal portions. 



6. Dorsal fins two in number: the first opposed to the ventrals; the 



second a short distance in advance of the anal. 



7. Caudal fin, heterocercal. 



8. Scales thick, covered with ganoine and finely punctate. 

 Carboniferous and Permian. 



The Permian species of Megalichthys were originally described by Cope 

 as a new genus, Ectosteorhachis. The distinction between this genus and 

 Megalichthys, according to him, consists in differences in the form of the 

 vertebral centra. "Both Agassiz and Huxley describe those of Megalichthys 

 as completely ossified and as biconcave. In Ectosteorhachis they are repre- 

 sented by annular ossifications resembling somewhat those of the stegoceph- 

 alous genus Cricotus, but with a larger foramen Chordce dorsalis" (25, p. 56). 



Regarding this distinction it may be said that the vertebrje of Cope's 

 Ectosteorhachis do not diflter markedly from those of Megalichthys as figured, 

 for instance, by Wellburn.* In both they are narrow rings, but those in 

 Cope's specimen (see plate 30, figs, i, 2) are not well enough preserved to 

 make it absolutely certain that they were complete, and not open, above. _ 



In all other respects, so far as the state of preservation of Cope's speci- 

 men allows of comparison, Ectosteorhachis and Megalichthys are the same. 

 Hence the latter name should be employed for Ectosteorhachis. \ 



* Proc. Yorkshire Geol. and Polytechnic Soc, 1900, pi. xix, fig. F. 



t Dr. O. P. Hay has pointed out (54, p. 362) that the name Megalichthys was first applied to the fishes 

 generally known as Rhizodus. And hence Rhhodus should, properly, be called Megalichthys, because of priority; 

 and the genus generally called Megalichthys should have its name changed to Parabatrachus Owen, which is an 

 available synonym. But in view of the confusion which would result in thus reversing a usage which has been 

 in vogue for eight decades and has become thoroughly established in the science, the writer deems it best to 

 retain the name Megalichthys in its present general usage. 



