VEBTEBEATES. 301 



condition it is obtusely conical, as are also the lateral denticles ; the 

 entire surface of the crown may present a fine granulose punctation, 

 generally, however, this structure is visible only in worn surfaces, the 

 lateral extremities of the crown being enveloped in a polished enamel- 

 like layer. 



The present form was first brought to our notice by Mr. Springer, 

 and subsequently Mr. Wachsmuth made interesting accessions to 

 the material illustrating the species, from the same locality. It is dis- 

 tinguishable from Orodus mammillaris, IS. and W., with which it is 

 somewhat closely allied, by the less regular and stronger radiating 

 ridges in the coronal prominences, and which are more delicately decus- 

 sated instead of being strongly beaded or nodose, as in that form. In 

 their perfect condition the teeth of this species are amongst the most 

 beautiful and highly wrought of the numerous species of the genus; 

 and even when imperfect from long use or abrasion, they may be in 

 most cases recognized from the above named species, and readily so 

 from other species in the same and succeeding formations. 



Position and locality : Not uncommon in the lower fish-bed of the 

 Kinderhook formation ; Burlington, Iowa. 



Orodus D^edaleus, St. J. and W. 



PI. VI, Fig. 7, 8. 



Teeth somewhat variable in form, of medium or small size, attaining 

 .7 inch in length. Large median teeth laterally elongated, nearly 

 straight, and moderately arched vertically. Base relatively shallow, 

 obliquely expanded and rapidly beveled to a thin edge behind, the 

 opposite side presenting a broad channel, which separates the plane 

 inferior surface from the crown ; the crown exceeds the root in breadth 

 and hight, forming in the middle a strong symmetrical conical promi- 

 nence, which is strongly distended toward the base behind and in front, 

 where it terminates in a slight node, and is abruptly defined from the 

 lateral wings, which extend on either side in nearly linear direction, or 

 very gradually converging to the rounded extremities, which are slightly 

 deflected posteriorly; the crest and apical point are submedian, or 

 situated nearer the outer margin of the crown, more regularly and 

 broadly convex posteriorly than in front, in the lateral portions of the 

 crown produced into a series of well-defined tuberculations, which are 

 ornamented with delicately decussated radiating ridges, two or three of 

 which are continued downward from each cone and merged into the 

 irregularly plicated or reticulated basal border, which is more coarsely 

 developed in the outer margin and somewhat closely resembling the 

 plicated basal margins in 0. plicatus ; the large central cone is beauti- 



