270 New Species of Crinoidea from the 



In the centre of the ray between the brachial plates 

 there is an elongate interbrachial plate, sometimes reach- 

 ing down so as to truncate the top of the third radial 

 plate. First anal ])]ate nearly equal to the first radials, 

 hexagonal, supporting two smaller plates in the second 

 range, five in the third range, with five or six small plates 

 irregularly placed above. Surface of plates strongly convex, 

 marked by a series of ridges passing from plate to plate, 

 but becoming obsolete near the middle of each, giving an 

 appearance as if the plates had been worn. 



This species is most nearly related to A. sexarmatus 

 (1st Supp. Iowa Geol. Rep. p. 21) in general form and 

 surface markings ; but differs in being much wider in pro- 

 portion to the height, with plates more regularly convex, 

 and a different arm formula. 



Geolog-ical formation and locality. Burlington lime- 

 stone, Burlington, Iowa. Collection of C. A. White. 



Actinocrinus nnispina (n. s.). Body sub-turbinate, ab- 

 ruptly spreading from the third radial plates, and be- 

 coming somewhat pentalobate from the projection of the 

 arm bases, truncate at base, and moderately excavated for 

 the attachment of the column ; dome depressed-convex, 

 surmounted by a long, slender, sub-central spine. Basal 

 plates short, thickened at the lower margins, forming a 

 slightly projecting rim around the base of the cup. First 

 radial plate of moderate size, wider than high. Second 

 radial plates quadrangular, twice as wide as high. Third 

 radial plates short, pentagonal, wedge-form above, support- 

 ing on each side, in the postero-latcral rays, a large, supra- 

 radial, bifurcating plate, which supports on each side a 

 brachial plate, giving four arms to each ray; while on the 

 anterior and antero-lateral rays the brachial plates rest di- 

 rectly on the third radial plate, giving two arms to the rays ; 

 making the brachial formula sIj := 14. 



Interradial series consisting of three plates each ; the 



