572 THE CRINOIDEA CAMEEATA OF NORTH AMERICA. 



a lateral projection, or sort of elongate node, -which stands obliquely up- 

 ward, and gives to the lower part of the arms a zigzag outline. The 

 succeeding plates are biserial, and of these the three or four lower ones 

 are considerably higher than those above. The upper margins of the arm 

 pieces project slightly over the lower margins of the succeeding ones, the 

 sides are serrated, and the lines of union between them somewhat waving. 

 The three or four proximal pinnule joints are provided with moderately long 

 hooks. Regular interbrachials : 1, 2, 2 ; the first very large, rising to the 

 middle of the second costals, the two of the upper row quite minute. Anal 

 plate as long as, but narrower than the radials, followed by 2, 3, and 3 pieces. 

 Interdistichals one. The grooves between the rays extend up almost verti- 

 cally to one half the height of the tegmen, and are paved by rather large, 

 flat pieces ; while the orals and ambulacral plates are spiniform. Orals 

 pushed out far to the anterior side ; they are comparatively small and in 

 close contact ; the ambulacral plates arranged in alternate rows. Anal tube 

 nearly central, moderately large, and composed of spinous plates. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa, 

 Sedalia, Mo., and Lake Valley, New Mexico. 



Actinocrinus gracilis W. and Sp. (nov. spec). 

 PlateLVI.Fig.il. 



Approaching A. temdsmlptus, but a smaller species, and having a much 

 larger number of arms ; also the ornamentation of the plates more obscure. 

 Dorsal cup bowl-shaped, the sides to the top of the distichals slightly convex, 

 then bending abruptly outward ; the plates a little tumid, covered by faint 

 radiating strice and well defined ridges, the latter following the rays, and 

 forming deep depressions at the interdistichal spaces. 



Basals small, with a slightly projecting rim. Eadials one third larger 

 tlian the costals, and both wider than long. Distichals 2 X 10. Three bifur- 

 cations occur in the calyx, and one or two in the arms, all taking place from 

 the second plate, and all above the first axillary from one side only, the oppo- 

 site sides giving off a free arm. Arms from eight to ten to the ray, quite 

 slender, a little wider at the upper end than at the lower ; the three or four 

 proximal plates of each arm long and cuneate, and their widest sides, toward 

 the upper end, provided with a short lateral node, which gives to the lower 



