FOSSILS OF THE KEOKUK GROUP. 509 



we have no doubt in regard to the propriety of separating such species 

 from the typical forms of PeHtremitea. Our species has somewhat the 

 general form and appearance of P. Ece-meri of Shuinard (Missouri Rep., 

 pi. bj figs. L'". L'&, 2c, 2<Z,) but differs too widely to render a detailed 

 comparison necessary. 



Locality and position Keokuk division of Subcarbouiferous series; 

 near Warsaw, Illinois. 



GENUS PKOTASTEK, Forbes. 

 PROTASTER? GREGARIUS, M. and W. 



PL 16, Fig. 5. 

 Protatter gregarius, MEEK and WORTHED. Proceed. Acad. Nat. Sci., Phila., 1869, p. 169. 



THE disc of this species is circular in outline, slightly 

 convex above, and measures from 0.20 to 0.30 inch in di- 

 ameter. In most cases it looks as if merely covered by a 

 smooth, niembranaceous integument. Some casts of its 

 external surface, however, seem to show traces of flat, 

 nearly smooth, imbricating scales above. The five arms 

 are slender, flexible, and rather long in proportion to 

 breadth. In a specimen with a disc measuring 0.25 inch 

 in breadth, the diameter of the arms near the disc is only 

 0.05 inch. Xone of the specimens show the entire length 

 of the arms, though some fragments of them were seen 

 lying detached in the matrix, about 0.55 inch in length, 

 without being complete at either end. From the breadth 

 and gradual taper of these, it would seem probable that 

 when entire they may have been 0.75 to 1 inch in length. 

 Their impressions in the matrix give no indications of a 

 longitudinal furrow along the under side, but show that 

 there were about six pairs of arm pieces in a length of 0.16 

 inch. These pieces appear to be nearly though not exactly 

 opposite, and each one provided below with a compara- 

 tively large, round, deep pit, or pore, near the middle of its 

 anterior side. Along their lateral margins there appear to 

 be impressions in the matrix of very small spines (one to 

 each arm piece), though if such, they must have been ex- 



