INVERTEBRATES. 



247 



Fig. 26. 



The specific name was given in honor of Prof. J. G. Nor- 

 wood, of the University of Missouri. 



This species will be distinguished from the last, not only by its larger size, 

 and more robust habit, but particularly by having the two divisions of each 



ray, after they divide on the 

 last primary radial, continu- 

 ed on for some distance, 

 closely united, instead of ab- 

 ruptly diverging. Its sub- 

 radial plates also appear to 

 be widely different, though 

 fchey seem to be somewhat 

 abnormal in their form, in 

 the specimen from which our 

 diagram is made out. 



Since seeing a specimen 

 of Onychocrinus exculptus, of 

 Lyon and Casseday, sent on 

 to the Chicago Academy of 

 Sciences, by Mr. Lyon, we 



Onychocrinus Norwoodi. (Nat. size.) SUSpect that the form Under 



This diagram shows the subradial, radial and some of the „_„„: J i; , 



interradial pieces, as they appear to be arranged in a distorted Consideration may prove to 



Srciuon.' wUh the radial SeneS ° Ut a " Ule bey ° nd the firstbi "be a variety of the same. 

 Yet as it presents a greater irregularity in the size and form of the subradial 

 pieces, and some differences in the form of the first radials, we have concluded to 

 retain our name until we can have an opportunity to compare better specimens. 

 Locality arid position : River bluff near the south line of Monroe county, 

 Illinois; Keokuk division of the Lower Carboniferous series. 



ECH1NOIDEA 



PERISCHOECHINIDJE. (See page 225.) 



Genus OLIGOPORUS, M. and W. 



(ohyoq, few; xopoi;, a passage.) 



Synon. — Melonites (sp.), Meek and Worthen, Sept., 1860. Proceed. Acad. Nat. Sci., 



Philad., p. 397 ; (not Owen and Norwood, 1846). 

 Oliffoporus, Meek and Worthen, Sept., 1860. Proc. Acad. Nat. Sci., Philad., p. 474. 



The specimen upon which this genus was founded, consists 

 of two of the ambulacral series, and one entire intervening 



