29 



was slightly elevated, but the summit is injured in all of our 

 specimens. There are no ovarian pores shown, in any of our 

 specimens. 



This is the only species of Megistocrinus bearing seventeen 

 arms so far as known, and, therefore, need not be compared 

 with any other to distinguish it. It would seem to be most 

 nearly related otherwise to M. expansus. 



Pound by Geo. K. Greene, in the Hamilton Group, near 

 Charleston, Indiana, and now in the collection of Wm. F. E. 

 Gurley. 



STEGANOCRINUS SPERGENENSIS, n. Sp. 



Plaie II, Fig. 4, azygous view; Fig. 5, opposite view; Fig. 6, basal 

 view; Fig. 7, summit view. 



Species medium or above medium size. Calyx obpyramidal, 

 rather broadly truncated, pentagonal, and stelliform, as seen 

 from above, in consequence of the horizontal, rigid extension 

 of the five radial series. The abrupt, horizontal extension of 

 the radial series commences at the top of the third primary 

 radials, which commence curving outward from the calyx, 

 while the interradial areas begin to curve gently in, toward 

 the vault. Plates thick, very nodose and pyramidal. They 

 are sculptured so as to depress the angles of the plates. 

 Column large and round. 



Basal s form an hexagonal cup, more than twice as wide as 

 high. Plates stand upright, and each extends a cuneiform end 

 below the end of the column. Each plate is more than twice 

 as wide as high and longitudinally furrowed on the surface, 

 and the sutures are beveled. The first radials are the largest 

 plates in the body, and each one is furrowed from the central 

 node toward the angles and the basal plates below. A little 

 longer than wide, three hexagonal, two heptagonal. Second 

 primary radials less than half as large as the first, sculptured 

 in like manner, wider than long, and hexagonal. Third primary 

 radials a little smaller than the second, curve outward so as to 

 sharpen the angles of the pentagonal calyx, heptagonal axillary, 

 and support on each upper sloping side a single secondary ra- 

 dial which is axillary and supports on each upper sloping 

 side the tertiary radials. The tertiary radials are preserved as 

 far as the third plate, in our specimen, and to this extent and 

 doubtless for several plates beyond they are consolidated in 

 each series so as to leave no free arms. The two third radials 



