VERTEBRATES. 323 



from the teeth of A. variabilis, of the Upper Coal Measures. A tooth 

 of one of the lateral rows, probably anterior of the median row, is 

 illustrated PI. 6, fig. 16 a, b. c, d, showing enlarged views of the vari- 

 ous aspects of the tooth, which was also from Iowa, in a stratum a 

 little above that whence the preceding specimen was obtained. While 

 the figure 18 a, b, c, PI. 6, shows a tooth obtained by Mr. Fuller 

 from the shales overlying coal No. 5, near Springfield — a horizon proba- 

 bly nearly corresponding to the lower coal bed of the Middle Coal 

 Mt-asures of the Iowa survey. 



We also possess an interesting specimen preserved in a nodule from 

 Mazon creek, which apparently shows the remains of the entire cranial 

 and jaw cartilages of a fish of the present species, but which is in so 

 crushed and distorted a condition as to afford little additional informa- 

 tion. From the size of the teeth and the traces of the extent of the 

 jaw, there would appear to have been comparatively fewer rows than 

 obtained in the species A. variabilis; but further than this the speci- 

 men scarcely affords more than conjectural evidence on those more 

 important details of the arrangement and character of the teeth of the 

 opposite jaws. The cartilages present the appearance of minutely 

 reticulated sheets, the substance of the semiosseous matter having been 

 quite dissolved, leaving in relief the mineralized interstices, the aper- 

 tures having the same elongated outline described in connection with 

 the cartilages of A. variabilis under the preceding generic notice. 



Position and locality : Specimens of the teeth of the above described 

 form are known to occur in the lower strata of the Middle Coal Meas- 

 ures of southern central Iowa, also in nearly the same or subjacent 

 horizons of the Lower Coal Measures of Illinois, near Springfield, 

 Bloomington, and Mazon creek, in Grundy county. 



Agassizodus corrugatus (N. and W., sp.j 



PI. 8, Fig. 24. 

 Orodus corrugatus, NEWBEEBTand Worthen, 1870, m. Rep., vol. IV, p. 358, PI. Ill, Fig. 18, 18a. 



Our collections afford a few detached teeth from various localities and 

 horizons, representative of the species formerly described by Messrs. 

 Newberry and Worthen under the name Orodus corrugatus, a brief 

 notice of which is here offered. The original specimen was obtained 

 from a position referred to the lowest workable coal bed of the Lower 

 Coal Measures, near Alton, Illinois. Mr. Fuller obtained from the 

 shales of coal No. 7, near Danville, a tooth of one of the median rows 

 of the same species, while Mr. Alex. Butters procured from the roof 

 of coal No. 5, near Carlinville, teeth also probably referable to the same 

 species. But one of the most interesting discoveries in this connection 



