150 PALEONTOLOGY OF ILLINOIS. 



Geological position and locality: Warsaw limestone ; Jersey county, 

 Illinois. 



DELTODUS OCCIDENTALS ? (Leidy, sp.) 



PI. IX, Fig. 9-10. 



Compare Deltodus occidentalis, (Cochliodus occidentalis), Leidy, 1856. Trans. Am. Phil. 

 Soc.. XI, (2d ser.) 



Deltodus stellatus, NEWBEBBY and WOETHEN, 1866, 111. Geol. Bur., II, p. 97, PI. IX, f. 3-4. 



The collection from the Warsaw and St. Louis formations contain 

 rare examples of the teeth of both the mandibular posterior and 

 median^forms and of the maxillary posterior form of a species 

 closely^allied^ to, if indeed it proves not to be identical with, Delto- 

 dus occidentalis, (Leidy sp.) so numerously represented in the Keo- 

 kuk limestone. The Warsaw specimens, of which a single example 

 of the posterior tooth of the upper and lower jaws respectively has 

 been obtained, though fragmentary, present so close a resemblance 

 to the Keokuk species that were their stratigraphical derivation not 

 known they would without hesitation be relegated thereto. The 

 maxillary tooth (Warsaw) does not show quite as angular coronal 

 ridge, but in the outline and coronal contour in other respects it is 

 most intimate in its relations with 'that species. The mandibular 

 tooth (Jersey county) preserves only part of the middle or elevated 

 portion of the tooth, the borders and extremities being mutilated, 

 showing the general characteristics save the longitudinal ridges at- 

 tribuiable to the Keokuk teeth. In size they are a little larger 

 than the prevailing dimensions attained by the teeth of that species. 

 The St. Louis specimens are even more like the Keokuk teeth so 

 far as it is possible to judge from the few examples thus far ob- 

 tained. The collection of Mr. Van Home contains a fragment of 

 the mandibular posterior tooth, from Alton, and Prof. Worthen has 

 obtained from the same horizon in Monroe county, an almost entire, 

 though somewhat crushed and distorted, example of the opposed 

 tooth belonging to the left ramus of the upper jaw, in which the 

 keel along the crest of the coronal ridge is well shown. The char- 

 acter of the punctse is also very similar to the Keokuk teeth, both 

 of the specimens here alluded to being a little under medium size 

 as compared with the Keokuk examples. 



