312 PALAEONTOLOGY OF ILLINOIS. 



remarkable fish, consisting of a part of the jaw preserving about three 

 hundred teeth in their natural position, and which was obtained from 

 Upper Coal Measure strata in Osage county, Kansas. Subsequently, 

 or late in the following January (1864,) Mr. Springer, while passing 

 through Topeka, chanced to come upon another specimen, which he 

 kindly forwarded to Cambridge, the examination of which, together 

 with the fact that the latter specimen was derived from the same locality 

 as that reported by Prof. Mtjdge, led us to suspect that the two speci- 

 mens might prove to be fragments of one and the same individual — an 

 inference which was most couclusively confirmed not long thereafter, 

 on bringing the two specimens together. The former proved to be 

 about two-thirds the posterior portion of what appears to be the left 

 ramus of the mandible or lower jaw, the latter apparently completing 

 the anterior prolongation of the ramus, besides showing along the inner 

 margin, though much displaced by compression, a series of teeth belong- 

 ing to five or six of the anterior rows of the opposite ramus. But the 

 posterior portion of the right ramus has been broken away, and it is 

 apparent only a few teeth belonging to consecutive rows from the sym- 

 physis backward remain of what constituted this side of the mandible. 

 Considering the left ramus, which apparently presents quite the 

 entire dentition of this side of the jaw, the specimen exhibits the pos- 

 terior two-thirds, or the teeth from the first row in advance of the row 

 of large median teeth, in the normal condition as refers to the natural 

 relative position of the rows ; but in the anterior portion of the ramus 

 the rows towards the inner margin have been displaced or crowded for- 

 ward so as to give to the vertical or symphysial line a reversed deflec- 

 tion approaching that of the postero outer dentary border. The above 

 features of the ramus are well shown in fig. 1, PI. 8, which besides show- 

 ing the accidental displacement or spreading of the rows of teeth above 

 alluded to, also shows the ramus much flattened, so as to obscure the 

 convoluted inrollment, characteristic as well of the Gestracionts, giving 

 to the jaw almost precisely the same appearance the spread-out diagram 

 of the dental armature of Cestracion would present, as obtained by 

 stripping off the teeth and spreading them upon a flat surface. Hence, 

 in attempting the restoration, (PI. 8, fig. 22,) it is obvious that sufficient 

 allowance may not have been made for the inrollment of the anterior 

 portion of the jaw, thus producing an outline more obtusely angular in 

 front than may have obtained in reality. Yet, compared with the mod- 

 ern Cestracion, the jaws of the remarkable fish under consideration 

 were doubtless less acutely produced forward, and in this particular 

 holding a mean between its modern representative and some of the Bays 

 (e. g. Trigon) iu the relative obtuseuess of the anterior extremity of the 

 jaws. But the resemblance here ceases. In all other respects, as the 



