VEETEBEATES. 347 



be recognized as a group, however variable the individuals, and this 

 fact has led to their being noticed, provisionally, under a distinct head. 

 "While the present form presents all the variability observed in the 

 preceding and above mentioned forms, it is distinguished by the appre- 

 ciably less robust proportions, though attaining the same size. The lat- 

 eral extremities are more acutely rounded, and there is a very apparent 

 increase in the number of coronal folds, especially along the concave 

 crown face, although in this latter respect there is noticeable very con- 

 siderable variation — many examples closely agreeing with the Keokuk 

 teeth in possessing only three or four imbrications, while in some extreme 

 example they attain double the ordinary number, and when strongly 

 developed they increase by bifurcation, and more rarely by implantation ; 

 the folds along the convex face are also very like the above form, rang- 

 ing in number from two to four, often interrupted at the median line by 

 the more or less angular ridge of the principal cone ; the median prom- 

 inence is also quite variable in shape, always more or less eccentric, 

 laterally deflected, the apex produced over the concave face, generally 

 laterally compressed, though sometiuies presenting a remarkably pro- 

 duced, symmetrical prominence vertical to the horizontal plane of the 

 crown; the lateral portions of the crest exhibit the same variableness 

 in the distinctness of the denticiilations, which are always present in 

 well-preserved individuals, while the body of the crest is compressed, 

 low, and striking the convex margin from which it is separated by the 

 shallow intervening sulcation — rarely traversing the crown centrally. 

 The base is the same as in the preceding and above named forms, outer 

 and inner margins angular, shallowest beneath the concave face, inferior 

 surface flattened and beveled as in the above. The coronal surfaces are 

 smooth and polished, but in worn specimens coarse punctae appear in 

 the abraded spaces ; in many teeth either one or other, sometimes both 

 surfaces are ornamented with a delicate tracery of thread-like lines 

 which ascend more or less obliquely from the upper border of the coro- 

 nal belt, becoming obsolete near the crest. 



Eepresentatives of the second variety, as alluded to in connection 

 with the Keokuk form, have escaped notice, and this seems not a little 

 singular, taking into consideration the comparative abundance of the 

 material in the present instance. However, the collections contain teeth 

 in which the median cone forms a relatively inconspicuous prominence, 

 and the lateral elongation is an approach, at least, to the linear outline 

 of the above referred to form. 



The third variety is also known from but few examples, which present 

 the same general outline and contour, but which are distinguishable 

 from the Keokuk form by the undulated or plicated and, perhaps, ver- 

 tically more plane convex crown face, the angle in the convex face of 



