VERTEBRATES. 65 



Figure 6, 6 a, represent the top and side view of a medium specimen, natural 

 size. 



Formation and locality: Burlington limestone, Burlington, Iowa. 



Orodus ornattjs, N. and W. 



PI. IV, Figs. 7, 7 a, 8, 8 a. " 



Teeth small, laterally elongated, with a prominent central 

 cone, and a more or less conical outline; crown highly orna- 

 mented with numerous prominent caringe. Of these, ten or 

 more radiate from the summit of the central cone, covering its 

 sides with their tortuous branches. From the central cone a 

 sharp and prominent crest runs down to either extremity 

 along the median line. In some specimens this crest is broken 

 up into numerous small, lateral cones, which are ornamented 

 like the principal one, with radiating caringe. In other speci- 

 mens these secondary cones are scarcely developed, but the 

 crest is .serrated, when seen in profile, by the outlines of the 

 numerous ridges which cross it. The root is usually slightly 

 narrower than the crown, and of equal height, coarse, and 

 porous. A transverse profile shows it to be in most specimens 

 oblique to the crown. 



These are highly ornamented teeth, the crown being elaborately sculptured 

 in every part. They vary much in size, and somewhat in form, the larger ones 

 being laterally long and narrow, from 6 to 7 lines in length, while the smaller 

 ones are half as long, but thicker in the central part ; when seen from above 

 often presenting a sub-triangular outline. By their general aspect they remind 

 one of Orodus ductus, Ag., (<5p. Cit. p. 96, Tab. 11, fig. 1-4,) but they are 

 much smaller, and the ornamentation is more elaborate and of a different pat- 

 tern. 



Figures 7 and 7 a, represent a larger and smaller tooth, each viewed from 

 above, magnified to two diameters. Figures 8 and 8 a, crown and side view 

 of another small specimen, natural size. 



Formation and locality : Keokuk limestone, Warsaw and Nauvoo, Illinois. 



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