DESCRIPTIONS OF SOME NEW CRINOIDS. lOI 



Vault around the oral pole composed of com])aratively large plates, 

 ornamented with large granules or irregular nodes. Central dome- 

 plate nodose; ])roximal plates of larger size and more nodose. The 

 principal radial dome-plates are strongly nodose ; they connect with 

 several smaller ones, which together form a kind of triangular elevation 

 toward the arm bases. Anal aperture sub-central, extended into a 

 proboscis which consists of a slender tube of rather thick plates. Col- 

 umn round, composed of equal joints, thickened in the middle, thinned 

 at the outer edges. Central canal round. 



The surface markings are by ridges of uniform strength throughout. 

 At the base of the calyx they form a pentagon, the angles of which 

 rest just above the center of the first radial. From this point they 

 traverse the center of each plate in the radial series, forming with the 

 side of the pentagon a large hexagonal figure, the most noticeable 

 feature in this species. They connect in single or double lines the 

 center of each radial with the center of the figure, which is also the 

 center of the first interradial. From a small cup a»^ this point two or 

 three parallel ridges pass through the second interradial. 



Geological position, locality, etc.: Associated with the preceding spe- 

 cies, this was obtained by the writer from rocks of the age of the 

 Hamilton group, in the neighborhood of Alpena, in Xorthern Michi- 

 gan, the type specimens being in his collection. 



