BATOCRINID^. 505 



which one of the arms is luideveloped, a peculiarity which we have observed 

 occasionally also in other species of this genus. 



Agaricocrinus Sampsoni S. A. Millek. 

 Plate XLYI. Fig. S. 



1893. S. A. Millek; Adv, Sheets IStli Rep. Geol. Surv. ludiana, p. 20, Plate 3, Pig. 8. 



A moderately small species, remarkable for its massive arms, which are 

 proportionally heavier than in any other species known to us. Calj'x appar- 

 ently short ; the dorsal cup slightly convex ; the basal portions flat or very 

 little concave ; the interradial spaces rapidly curving upwards, so as to give 

 to the cup a pentangular outline. 



Basals small, but extending beyond the sides of the column. The radials 

 the largest plates of the calyx, wider than long ; their sloping lower faces 

 more than twice as long as the corresponding upper ones. First costals sub- 

 quadrangular, short, but longer than figured by Miller. Second costals 

 a little longer than the first, irregular in outline, the upper angle obtuse. 

 Distichals one, as large as, or larger than the axillary costals, more than 

 twice as wide as long, wedgeform, the larger outer ends bending inward. 

 Arms two to the ray, massive, gradually tapering, biserial from their origin ; 

 those of the same ray suturally united as high as the second row of plates ; 

 the arm joints rather long and slightly convex. Eegular interbrachials one, 

 moderately large, pentangular, a little longer than wide. Anal plate one 

 third narrower than the radials, but somewhat longer ; the three plates of 

 the second row narrow ; the two outer ones cuneate, their wider ends resting 

 against the sloping upper faces of adjoining radials; the sides of the middle 

 plate almost parallel. Ventral disk not visible in the specimen. 



Horizon and Locality. — Chouteau limestone, near Chouteau Springs, Mo. 

 Type in the collection of Mr. F. A. Sampson. 



EemarJcs. — The type specimen, which Mr. Sampson was kind enough to 

 send us for examination, lies upon a slab with its arms spreading horizon- 

 tally, so that its whole ventral side is covered by matrix. We regard 

 Agaricocrinus germanus and A. cJiouteauensis, both described by Miller, of 

 which only the calyx is preserved, as identical with this species; the former 

 being a young specimen, the latter, a more adult one. 



