322 PALJ3CXNT0L0UT OF ILLINOIS. 



opposite face. The base is relatively shallow, stout, in depth about 

 two- thirds the Light of the crown, and proportionately thick antero- 

 posterior^. 



The little tooth above described, which has apparently never been 

 brought into use for triturating purposes, and therefore in perfect con- 

 dition, probably belonged to one of the lateral rows, either anterior, or 

 more likely posterior to the median row, and indicating a species in 

 this respect quite strongly contrasting in its dentition to that previously 

 noticed. However, the specimen may have belonged to a median row, 

 but in either case its distinctive peculiarities are too marked to suggest 

 identity with the other forms of the genus. It probably belonged to a 

 young fish, else it represents a species which never attained the formi- 

 dable size of the fish which bore the teeth of A. variabilis. 



Position and locality : From strata about 100 feet above the Mahon- 

 ing sandstone, or lower part of the Upper Coal Measure series of the 

 Appalachian region ; near Morgantown, West Virginia. The above 

 strata have afforded Prof. Stevenson a few very interesting ichthyic 

 remains, some of which are described in the present report. 



Agassizodtjs scittjltjs, St. J. and W. 



PI. 6, Fig. J6 a, b, c, d, 1? a, 18 a, b, c. 



This form is represented by very small and minute teeth prevalent in 

 strata of the Middle Coal Measures, or upper part of the Lower Coal 

 Measures, of which only a few detached teeth are thus far known to us. 

 These would indicate some variableness in shape, but no more than is 

 consistent with their relative position upon the jaws, and of which it is 

 believed we have examples pertaining to the median and lateral rows. 

 The superficial characters presented by the various forms at present 

 known are illustrated in the figures in PI. 6, aud need not be detailed 

 in the text, further than to remark their distinguishing characters as 

 compared with the previously noticed species. The teeth of the sup- 

 posed median rows of this form bear a somewhat close resemblance to 

 the unique Virginia example noticed iu the foregoing description, only 

 the coronal faces are more strongly ornamented, and the posterior face 

 more gibbose and abruptly iubeveled to the basal line below. The 

 . opposite face between the prominent vertical buttresses exhibits traces 

 of what appear to have been transverse striae; the latter feature is 

 indistinctly shown in a group of three teeth from Iowa, although it is 

 not represented in the figure given of the specimen, PL 6, fig. 17 a. 

 The relative shallowness of the base (which is made to appear of greater 

 depth than is really the case in the figure just cited, as also in fig. 18,) 

 in all these examples, together with their small size, distinguish them 



