40 



HYDREIONOCRINUS SANCTILUDOVICI, Worthen. 



Plate VI, Fig. 2, view of the type. 



Prof. Worthen, in Volume VIII of the Geo. Sur. of Illinois, 

 pa^e 98, gave a short description of this species, under the 

 name of "Eupacbjcrinus sanctiludovici," but did not illus- 

 trate it. We have figured the type of the species, which is 

 very fragmentary, as stated l)y Prof. Worthen, but from the 

 expanded summit of the vault and the short, strong spine, 

 shown on the right of the illustration, we suppose it to belong 

 to (he genus Hydreionocrinus, to which we have referred it. It 

 occurs in the St. Louis Group, at St. Louis, Missouri, and from 

 his imperfect description and our illustration, the species may 

 be identified. 



HYDREIONOCRINUS 8UBSINUATUS, U. Sp. 



Plate VI, Fig 11, azygous side view of the calyx; Fig, 12, 

 basal view of same specimen; Fig. IS, azygous side view 

 of another specimen, preserving part of the spi- 

 nous second radials; Fig. 14, basal view 

 of same specimen. 



Calyx depressed, saucer-shaped, slightly concave below, loniri- 

 tudinally concave on the ventral side; sutures distinct; surface 

 smooth. When viewed from above or below, hexagonal, in out- 

 line, by reason of the truncated first radials, and the concave, 

 wide azygous area. Column round. 



Basals form a pentagon one-half wider than the column, with 

 a central, columnar cavity surrounded by an external rim, for 

 the support of the attaching column. Subradials of moderate 

 size, three of them api^arently pentagonal, though as each one 

 abuts upon two basals, where there is an obsure angle, they 

 are really hexagonal. The two adjoining the azygous area are 

 heptagonal. They curve very sliahtly down to the basals, and 

 upward, toward the acute angles between the first radials. 

 They are not uniform in size or shape; the heptagonal plate 

 on the right of the azygous area is the wider, and the one on 

 the left the longer one. First radials twice as wide as high, 

 truncated the entire width abov(\ mucli thickened within, and 

 separated from the second radials, on the outer face, by a 



