440 PALEONTOLOGY OF ILLINOIS. 



GENUS DICHOCRIKUS, Munster, 1839. 

 DICHOCRLNTJS LINEATUS, M. and W. 



PL 3, Fig. 1. 

 Dichoerinus lineatus, MEEK and WOKTHEN. Proceed. Acad. Nat. Sci., Phila., 1869, p. 69. 



BODY ovoid-subglobose, about as wide as long, not round- 

 ed below, but abruptly tapering to the column ; widest near 

 the middle, and but slightly contracted above. Base form- 

 ing very nearly half the hight, and expanding rapidly, so 

 as nearly to equal at the top the greatest breadth of the 

 body ; margins faintly sinuous for the reception of the next 

 range of pieces; sutures a little furrowed, but anchylosed. 

 Radial pieces quadrangular, generally nearly or quite as 

 wide as long; sinus above for the reception of the second 

 radials shallow, rounding, and equaling about half the 

 breadth of the upper margin, marked 'with fine, radiating 

 striae at the outer margin. Anal piece as wide below as the 

 first radials, but narrower above, and slightly shorter; sub- 

 pentagonal in form, being but very obtusely angular in the 

 middle below. (Succeeding parts unknown.) 



Surface ornamented with numerous sharply elevated 

 lines slightly less than the furrows between. Of these 

 lines, on the base, a part near each lateral margin run par- 

 allel to the same, while other series further from the mar- 

 gins, although parallel with each other on each side of the 

 middle, run obliquely so as to connect with the lateral ones 

 and with each other along the middle, in such a manner as 

 to form tliree divaricating series on each piece ; near the 

 upper margins there are also traces of a few very fine, 

 crowded striae running parallel to the same. On the first 

 radial and anal plates there are also a few fine, transverse 

 striae near and parallel to the lower margins, while on 

 a triangular central space, with its most acute angle 

 terminating near the middle of the top, there are vertical 

 or slightly converging striae, of the same si/e as the divari- 



