42 University Geological Survey of Kansas. 



HYDREIONOCRINUS. 



de Koninck, Bull. Acad. Royale Belgique, viii, pt. n, p. 13, (1858.) 



Hydreionocrinus kansasensis. Plate VII, figs. 4-7. 



Hijdreionoerinus kansasensis Weller, Trans. N. Y. Acad. Sci., xvi, p. 

 '372, (1898.) 



Weller's description : " Dorsal cup depressed, nearly saucer- 

 shaped, more than twice as wide as high, truncated below. 

 The margins of all the plates, except the lateral margins of the 

 infrabasals, ornamented by narrow papillose bands parallel to 

 the sutures. Exclusive of the papillose bands the plates are 

 smooth. Infrabasals five, large, extending far beyond the 

 column, anchylosed into an irregularly hexagonal, nearly flat 

 disc, the sutures marked by slightly elevated ridges ; central 

 portion of the disc slightly excavated for the attachment of the 

 column, the excavation surrounded by a low ridge. Basals 

 five, four of them broader than high, spherical-triangular in 

 outline, in lateral contact only at the extreme lateral angles. 

 The posterior basal higher than wide, quadrangular in outline, 

 truncated distally for the reception of the special anal plate, 

 the lateral and proximal sides curved as in the four other 

 plates. Radials large, twice as wide as high, the three anterior 

 ones heptagonal in outline, the two posterior ones hexagonal. 

 The proximal sides concavely curved to conform to the curved 

 sides of the basals, the proximal angles meeting the distal angles 

 of the infrabasals and the lateral angles of the basals. First 

 brachials twice as wide as high, pentagonal in outline, bearing 

 upon the two upper sloping sides of the two main divisions of 

 the arms. Arms uniserial, the component plates broader than 

 long, except near the tips, rectangular in outline except the 

 axials, which are pentagonal. In the right posterior arm, the 

 only one known, each main division bifurcates several times, 

 the most posterior one showing ten divisions at the tip. Kadi- 

 anal nearly as large as the basals, pentagonal, higher than 

 wide, lying upon the truncated right posterior infrabasal and 

 between the posterior basal and the right posterior radial. 

 Special anal larger than the radianal, hexagonal, higher than 

 wide, lying upon the truncated posterior basal and between the 



