30 



a single series of long cuneiform plates that alternately pro- 

 ject for the support of coarse pinnules. The arms, therefore, 

 have quite a rough aspect. 



The azygous plates are alternately arranged. The first one 

 is pentagonal, rests between the superior sides of two subra- 

 dials and below the first radial on the right and abuts against 

 the second and third plates. The second azygous plate trun- 

 cates a subradial and abuts the first radial on the left and the 

 first and third azygous plates on the right. The third azygous 

 plate truncates an angle on the first plate and separates the 

 first radial on the right from the second azygous plate. Above 

 these the alternate arrangement is continued as far as the area 

 is exposed in either of our specimens. 



This species is distinguished by its saucer- shaped calyx, con- 

 vex and tumid plates and ten rough arms composed of long 

 cuneiform plates. It is one of the kind that has been referred 

 to Scaphiocrinus, on account of the arm structure, but it does 

 not agree with that genus, in the structure of the azygous 

 area, but on the contrary is, in that respect, a Poteriocrimis 

 to which genus we refer it. It will not be mistaken for any 

 other species. 



Found by the late Wm. McAdams, in the Kaskaskia Group, 

 in Monroe county, Illinois, and now in the collection of Wm 

 F. E. Gurley. The specific name is intended as a compliment 

 to the artist and palaeontologist who made the illustrations for 

 this Bulletin. 



POTERIOCRINUS LAUTUS, n. Sp. 



Plate II, Fig. 18, azygous side; Fig. 19, opposite view. 

 Species medium size. Plates angular, convex, rough. Calyx 

 saucer- shaped, more than three times as wide as high. Surface 

 granular. 



Basals hidden or nearly so by the column. Subradials about 

 as long as wide and forming a pentagonal disc very slightly 

 saucer-shaped. First radials twice as wide as long, pentagonal, 

 flattened centrally, truncated the entire width above and sep- 

 arated from the second radials or brachials by a gaping suture. 

 Second radials wider than long, constricted in the middle and 

 in four of the rays axillary, pentagonal and have steep upper 

 sloping sides for the free arms. The arms are composed of 



