VEETEBEATES. 321 



not to admit of its reference to the mandibular rows : no similarly 

 shaped teeth occur on the lower jaw, their marked sigmoidal curva- 

 ture, and the central position of the slight apical prominence, constitu- 

 ting the chief distinguishing features. Their comparatively slender 

 form would indicate that they belonged to the anterior rows, and it 

 would seem very probable that they constituted the row contiguous to 

 that of the median teeth of the right maxillary. In figures 15, 16 and 

 17, PI. 8, we may possess representatives of teeth pertaining to the 

 extreme posterior rows of the upper jaw, since the mandibular speci- 

 men from Kansas affords no similar teeth. On the other hand, the 

 latter specimen exhibits teeth in the extreme anterior rows unmistakably 

 like those represented in figures 18 and 19. 



The shagreen scales, and other semi-ossified fragments of the car- 

 tilaginous jaws which pertain to this species, have been mentioned in 

 the foregoing notice of the genus. 



Position and localities : So far as our data show anything to the con- 

 trary, the present species appears to be restricted to the Upper Coal 

 Measure strata, in which position authentic specimens from the follow- 

 ing localities have been obtained : LaSalle and Springfield, Illinois, at 

 both places above the horizon of coal Xo. 9 of the Illinois section ; Fre- 

 mont county, Iowa; Osage county, Kansas. 



Agassizodus Virginiantts, St. J. and W. 



PI. 8, Fig 23, a, b, c, d. 



A unique specimen of a tooth discovered by Prof. J. J. Stevenson 

 in the "Upper Coal Measures of West Virginia, seems to possess dis- 

 tinctive features, as compared with the forms prevailing in the Coal 

 Measure strata in the Mississippi valley, sufficient to establish its dis- 

 tinct specific character. The tooth in question is small in size, half an 

 inch in length, and about .30 inch in greatest hight. The crown is very 

 stout in its build, slightly arched backward, the crest forming an acute 

 angle, and regularly rising into the somewhat prominent, slightly eccen- 

 tric median cone, rounded and indexed at the extremities ; the posterior 

 face is considerably distended about midway between the basal line and 

 the crest, and besides the sharp ridges descending from the faint sec- 

 ondary cones half way to the base, and the delicate intermediate carinas 

 marking alike both sides of the crest, the inferior half of the surface 

 is ornamented by delicate, wavy vertical lines ; the anterior face pre- 

 sents six buttresses, which are relatively strong, three in the long 

 extremity, and two in the opposite extremity, with a wide space inter- 

 vening between them aDdthe median buttress — the inferior half of the 

 surface between the buttresses similarly ornamented as described in the 



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