BATOCEINID^. 443 



convex ; in some species quite prominent and the surface slightly rugose, in 

 others almost flat and perfectly smooth. Suture lines grooved. 



Base short, hexagonal in outline, rounded at the bottom, the colunni facet 

 slightly excavated, the interbasal sutures impressed. Radials wider above 

 than below, deeply notched for the reception of the first interbrachial, the 

 upper face concave. Costals rather large for the genus, together about equal 

 to the size of the radials ; the upper larger and generally heptagonal. Dis- 

 tichals two, smaller than the costals, the axillaries^ supporting 2X2 palmare, 

 and normally four arms to the ray ; frequently, however, the anterior ray 

 has but two or three arms, and an additional fixed distichal in place of pal- 

 mars. Arm openings directed obliquely upwards ; the interspaces separating 

 the rays a little wider and deeper than those between the openings of the 

 same ray. Arms from eighteen to twenty, long, rounded on the back, grad- 

 ually tapering but not infolding, and composed from the calyx up of two 

 rows of transverse pieces. Pinnules long and cylindrical. Interbrachials 

 from five to seven ; the lower wider than long, and generally not rising 

 to the full height of the second costals. There are two comparatively large 

 plates in the second row, and one in the third, followed by one or two 

 irregular pieces, which separate the rays at the arm bases. Anal plate con- 

 siderably longer than the radials, supporting three plates in the first, and 

 three to four in the second range ; the succeeding ones irregularly arranged 

 and interlocking with the interambulacral plates. Ventral disk depressed 

 conical. Orals and radial dome plates a little larger than the interambulacral 

 pieces ; arranged in the usual way. Anal tube stout and very long, rising 

 in some specimens as much as 6 cm. beyond the tips of the arms ; the plates 

 smooth. Column round, of medium size, the nodal joints rounded at the 

 edges, the others considerably narrower near the calyx, but attaining the 

 same width farther down. 



Horizon and Localiti/. — Lower Burlington limestone; Burlington, Iowa, 

 and at several places in Missouri. 



TyjJe in the (Worthen) Illinois State collection, Springfield. 



Remarks. — We regard Batocrinus cassedayanus M. and W., as a mere 

 variation of this species ; the plates, although more convex than in the typi- 

 cal form, are arranged in exactly the same way. 



