INVERTEBRATES. 97 



<ii:.Ms ACTINOCRINUS. Miller. 



AiTIXOTIMXUB LOBATUS. Hall. 



PI. Xn, Figs. 8-8a. 



Body large, urn-shaped below the arms, and conical above, the 

 dome gradually diminishing- into a strong ventral tube com- 

 posed of strongly protuberant plates. 



Masai plates nearly as large as the first radials, thickened 

 below so as to form a slightly projecting rim around the 

 column. 



First radials large, length and breadth nearly equal, hexagonal 

 and hepta-ronal : second radials about half as large as the first, 

 and hexagonal: third radials smaller than the second, giving 

 support to two brachials. These are succeeded by a second and 

 third series of small brachials of which there are four or more 

 to each ray. 



First interradial hexagonal, about the same size as the second 

 radial, succeeded by two smaller interradials, with a third and 

 fourth scries of still smaller interradials of three each. 



First anal plate smaller than the first radials, hexagonal with 

 two smaller hexagonal plates in the second series, three in the 

 third series, and four in the fourth. 



Surface of the plates traversed by ridges, which, joining to- 

 gether near the center of the plates, form short flattened nodes. 



Arms composed of a double series of short interlocking plates, 

 and, on one of the specimens figured, showing numerous bifurca- 

 tions. 



Position and locality: Keokuk limestone, Greene county, 111. 



Collector, Henry Talbot, Esq. 



No. 2583 of the Illinois State Museum. 



GEMS EUPACHYrUIM S. Meek and Wortheu. 

 EupACHYCRraus ORBICULAIUS. Hall sp. 



PL XIV, Figs. 



This species was described in 18GO, in the Boston Journal of 

 Natural History as ScapbJOCTMUS orbirnlurix. The following is 

 the original description: 

 -12 



