4- '^9 



Ilayclen.] *^^ [May 0, 



Description. — The base of the tooth is semi-elliptical in outline, ob- 

 tusely angular behind, with low protuberances rising at the angles upon 

 the superior inner margin, the outer margin interrupted by a broad, shal- 

 low sinus, at either angle of which, immediately beneath the smaller 

 lateral denticles, an obtuse node projects downward, similar to those upon 

 the upper opposite side of the root, the presence of which would seem to 

 have been designed to lend additional strength to the muscular attach- 

 ment of the tooth upon its cartilaginous support; median cone cervical, 

 regularly tapering, recurved, inequally compressed, with acute lateral 

 edges; striae sharp, interrupted, separated by wide plane spaces, less nu- 

 merous upon the strongly compressed anterior face, and confined to the 

 lower half of the cusp; lateral denticles two upon either side, strong, with 

 sharp cutting edges, and strong sharp strise or ridges. 



Breadth of base twice its length, and equal to the entire height of the 

 tooth. 



This species, so far as we at present know, is restricted to the Upper 

 Coal Measures. The single type specimen from which the species was 

 originally described, was found in the Upper Coal strata near Springfield, 

 Illinois; and in the pi'osecution of the geological survey of Iowa, Dr. 

 White has brought to light the same species from the Upper Coal Mea- 

 sures of the southwestern portion of the State. I have also found this 

 species in the same formation at Manhattan, Kansas. 



Compared with other species, the present one is probably more closely 

 related to G. mirabilis, Agassiz, from the mountain limestone, Ireland, 

 than with any other with which I am acquainted. It differs, however, 

 in being less robust, and more symmetrical in its general proportions. 



Formation and Locality: — Upper Coal Measures, bed 6, Nebraska 

 City section, Nebraska. 



Gekus DIPLODUS, Agassiz. 



DiPLODUS COMPRESSTJS, Ncwb. 



Beference.—l^ewherrj, Geol. Illinois, Yol. II, p. 60 ; PI. IV, fig. 2. 



The single specimen Diploclus in the collection is probably referable to 

 the form described by Dr. Newberry, under the name D. compressus. 



Description. — The tooth is of medium size; base slightly narrower than 

 long, broadly rounded in front, and terminating in an obtuse point be- 

 hind, under surface slightly raised in the middle, anterior extremity pro- 

 duced into a large obtuse tubercle projecting slightly outward and down- 

 ward, with a flattened, sharply defined, obovate pad-like projection upon 

 the upper surface of the posterior extremity, marked upon either side by 

 a shallow groove terminating above in a little pit, and which' is entirely 

 separated from the bases of the crown cusps, — in this latter respect, as 

 Dr. Newberry has remarked, offering marked contrast to D. gibbosus, 

 Agassiz, from the mountain limestone of Europe; cusps three, median 

 one rudimentary, slender, compressed, with finely crenulated lateral edges, 

 base well defined from the general surface and terminating in a slight 

 protuberance in the osseous root in front; the apices of the lateral cusps 



