27 



B. rotundus and B. oblatus. In form it appioaches B. rohmdus, 

 but that species has twenty-one ambulacral openings to the vault, 

 as follows: 5+4+4+4+4, while this species has twenty-three, as 

 follows: 6+4+4+4+5. They also differ in the regular and azy- 

 gous areas. It differs in form from B. oblatus, which has twen- 

 ty two arms, as follows: 5+4+4+4+5, and it differs in the azy- 

 gous and interradial areas. There is no reason why it should be 

 mistaken for either of these species. B. rotundus is the prevail- 

 ing form in Missouri, where this species is yet unknown; while 

 B. oblatus is the prevailing form in Iowa and some localities in 

 Illinois, where B. rotundus ilso occurs, and where this species is 

 also found. 



Found in the Burlington Group, at Burlington, Iowa. The 

 type is from the collection of S. A. Miller; other specimens are 

 in the collection of A. Albers. 



BATOCRINUS COMPLANUTUS, n. sp. 



Plate I, Fig. 19, azygous side; Fig. 20, opposite view. 



Species variable from below to above medium size. We have 

 specimens smaller and others larger than the one illustrated. 

 Vault smaller than the calyx. Calyx obconoidal, rapidly expanding 

 from the column to the arms. Ambulacral openings directed 

 above an horizontal line and not visible, in a basal view. (Surface 

 of the plates plain and smooth, some of them on the vault, some- 

 times slightly convex. 



Basals form a low, hexagonal cup, with re-entering angles and 

 having a round, hemispherical depression for the attachment of 

 the column. The cup is a little more than twice the diameter of 

 the column. First primary radials one-half wider than long, three 

 hexagonal, two heptagonal. Second primary radials about one- 

 third as large as the first, quadrangular, and about twice as wide 

 as long. Third primary radials a little larger than the second, 

 four hexagonal, one pentagonal, axillary, and in four of the rays 

 bear, upon each superior sloping side, two secondary radials, 

 the last of which are axillary and bear upon each upper sloping 

 side two tertiary radials, which arrangement gives to each of 

 these rays four arms and four ambulacral openings to the vault. 

 In the ray opposite the azygous area the third primary radial 



