86 PALEONTOLOGY OF ILLINOIS. 



heptagonal intersupra-radial plate rests on the adjacent edges 

 of the first supraradials. 



First interradial plates heptagonal or octagonal; the anterior 

 ones large, supporting two or three plates in the second and 

 third range each. First anal plate as large as the first radials, 

 strongly tuberculiform, supporting in the second range three 

 plates, and in the third range four, with some small plates in- 

 tercalated between the arms. Dome large, becoming proboscidi- 

 form. Surface granulose, the granules sometimes pustuliform. 



Column large, consisting of strong joints separated by thinner 

 ones, and, farther from the body, by two, three, four or more 

 thinner ones." 



In addition to the above description, I would add the follow- 

 ing: Ventral tube long, gradually tapering and rising symmet- 

 rically from the center of the dome, composed of massive hex- 

 agonal plates, nearly all of which are produced into a short 

 spiniferous node, and occasionally into a slender spine, half an 

 inch or more in length. About half the length of the ventral 

 tube above the dome a single row of six plates is replaced by 

 stout spines % of an inch in length, and about r> /ir> mcn i n Di- 

 ameter at the base. These long spiniferous plates probably sur- 

 round the anal opening. Above this the plates are less massive 

 and diminish in size to the apex. 



This fine species is only found in the Keokuk limestone, and 

 for the use of the specimen figured I am indebted to Mr. L. A. 

 Cox, of Keokuk, by whom it was kindly presented to the nuthor. 



GENUS POTERIOCRINUS, Miller. 



POTERIOORINUS SPINULIPERUS. (sp. UOV.) 

 PL XIV, Fig. 3. 



Poteriocrinus spinnUferns, Worthen, March, 1884. Bulletin No. 2 of the Illinois State 

 Museum of Natural History, page 27. 



Body of medium size, short, width three times as great as the 

 height to the top of the first radials; base depressed, under- 

 basals small and concealed under the first columnar joint. Col- 

 umn obscurely pentagonal near its upper extremity, becoming 

 round below, slender and composed of alternate thin and thicker 

 joints near the base, beyond which it is unknown. 



