VEETEBEATES. 317 



former name, the specimen figured (Vol. IV, PI. Ill, fig. 18,) preserving 

 four teeth of the median row, probably of the right ramus of the man- 

 dible, or left maxillary, besides three successive rows of two and three 

 teeth. Specifically, however, the latter species exhibits strongly con- 

 trasted characters in comparison with the former, in the more tumid, 

 spreading figure and tbe more elaborate tracery of the superficial coro- 

 nal ornamentation. One of the specimens figured by Messrs. New- 

 berry and Worthen, (PL IV, fig. 11,) which is referred to the former 

 species, exhibits in its lofty median summit, flanked by comparatively 

 slender, diverging lateral prolongations of the crest (which converge at 

 an angle of about 90°) a most striking contrast to the form generally pre- 

 sented by the teeth of this species. Neither of the magnificent series 

 of teeth from Kansas and Iowa, have representatives of the form here 

 referred to; and yet, from the symmetrical form of this tooth, it seems 

 very improbable that it is abnormal. It is possible that the anterior 

 portion of the upper jaw bore a single row of these cuspidate teeth, or 

 it may be the representative of a distinct specific form. The Iowa and 

 Kansas specimens, above described, are apparently specifically identi- 

 cal with the teeth here referred to. 



In a former volume of this Eeport, Messrs. Newberry and Worthen 

 described a tooth under the name Relodus clenticulatus (Vol. II, p. 81, PI. 

 V, fig. 6,) which was reported from the Keokuk division of the Lower 

 Carboniferous series. This unique specimen certainly possesses marked 

 affinities with the teeth of the genus under consideration; indeed it 

 might readily be mistaken for an abraded tooth from the anterior por. 

 tion of themedian row of acuminate teeth, showing the buttress-like pro- 

 jections in the anterior face, but possessing at the base of the posterior 

 crown face, beneath the eccentric median cone, a protuberance or cal- 

 losity, such as occurs in some forms of Helodus (Loplwdus, Eom.,) as well 

 as in Orodus. Since the above description was published, we have had 

 opportunity to examine large accessions illustrative of the ichthyic 

 fauna of the Keokuk epoch, but without meeting a solitary companion, 

 to the tooth here referred to. This naturally suggests the possibility 

 of some error in assigning the specimen in question to the Keokuk lime- 

 stone. 



With the single exception just alluded to, the present genus would 

 appear, for anything to the contrary furnished by present data, to be 

 confined to the Upper Carboniferous or Coal Measure period in our 

 earth's history, in the lower and upper members of which examples are 

 known to occur. It is not at all improbable, as suggested by Messrs. 

 Newberry and Worthen, that this group constitutes the representa- 

 tive of Orodus in these horizons, since only a single form of the latter 



