4CO PALEONTOLOGY OF ILLINOIS. 



ated about half way between the middle of the vault and 

 the anal side. 



The specimen from which our description is drawn up 

 only shows the body, the bases of the arms, and the pieces 

 connecting the latter to the second radials. These pieces, 

 forming the two main divisions of each ray, are in close 

 conta'ct out to where the second bifurcation takes place, 

 where the two main divisions diverge and separate. The 

 arm-bases in this specimen are quite slender. 



Another larger specimen in Mr. WACHSMUTH'S collection 

 (No. 215 &,) has the arms preserved. He thinks this not dis- 

 tinct from Dr. WHITE'S species, just described, though its 

 first radial pieces are longer in proportion to breadth, and 

 its arms apparently stouter; still it may be a variety of the 

 the same. It shows clearly four arms to each main division 

 of the rays, or forty to the whole series. Its arms are 

 rounded, and increase gradually in thickness from the base 

 to a distance of about 1.80 inches, and then gradually taper 

 for about 0.60 inch, at which point they are broken off in 

 the specimen, or in part curved in, so that their entire 

 length cannot be seen. 



Hight of a small specimen, 0.50 inch to top of iirst radial 

 pieces; breadth of do., about 0.41 inch. Other distorted 

 individuals seem to have attained twice the diameter of 

 that from which the above measurements were taken. 



The specimen from which our description was drawn np and our 

 figure prepared is one of those Dr. WHITE had before him in describ- 

 ing this species, and the characters given by him were in part taken 

 from it. For this reason we have preferred to figure this particular 

 specimen, instead of another in a better state of preservation, because 

 the latter (No. 215 &, mentioned above,) may possibly be distinct. 



As already mentioned in the remarks in regard to the relations of 

 that species, it seems to be most nearly related to P. Burlinytonemis, 

 but differs materially in size, the number of its arms, and other charac- 

 ters already mentioned. In size, and some other characters, it is more 

 nearly allied to P. Halli, Shumard, P. olla, Hall (not de Kouinck), but 

 if that species has been properly identified by all of the Burlington 



