254 SMITHSONIAN INSTITUTION 



height of calyx to width, I to 1.5; height of calyx to crown, 1 to 2; spread of 

 calyx from base, 1 to 3.2; height to width of crown, 1 to 0.7. Cross-section ob- 

 tusely decagonal, side outline curved. Base flush with column facet. Surface 

 smooth. Calyx plates flat or gently rounded, without median elevation. Sutures 

 sinuous, patelloid processes not prominent except in the arms. Height of crown 

 of large specimen, 65 mm.; of calyx 36; width 52; of base 13; of column at 

 lower end of expansion, 9 mm. Average of these dimensions in five specimens, 

 50; 25; 37; n.4;8. 



General arrangement of plates as in F. agassizi, but iBr less numerous, 

 RR and lower Br plates much shorter. Primibrachs 3. Height of B to R 

 to IBr, 1 :i :i.25. Height and width of successive plates in a large specimen: 

 B, 4 x 7; R, 4 x 9; IBr, 4x9; IIBn, 3x8; IIIBr, 2.2 x 5 ; IV Br, 2 x 4. IIBr, 

 3 or 4; numbers of successive orders of brachials as in agassizi. Above the third 

 bifurcation the outer ramus of each dichotom is much wider than the inner; 

 arms infolding at about fifth to sixth bifurcation, with probably more beyond. 

 Rays low convex, arms flat, usually abutting above iBr, though in smaller speci- 

 mens sometimes more rounded and slightly separated. The calyx is relatively 

 lower than in F. agassizi, and in the average of the specimens the crown more 

 slender and arms as usually exposed longer; the base and column relatively 

 broader. The column continues strong and cylindrical below the taper, with 

 simple alternation of thicker and thinner non-projecting ossicles, becoming more 

 nearly equal downward; it is preserved in one specimen to a length of 17 cm. 

 with no sign of cirri or roots, or change in diameter. 



This is the species of the western or typical Keokuk limestone beds along the Mississippi 

 River, being found at Keokuk, and various localities in Iowa, Illinois and Missouri, from 

 above Nauvoo to the mouth of the Illinois River in Jersey County. It is readily distin- 

 guished from its Burlington predecessors by the lack of nodose elevation of the plates, and 

 its shorter lower brachials ; but not so easily from F. multibrachiatus of the eastern Keokuk. 

 Hall's type is vertically crushed, and his figure did not disclose the base, owing to injury 

 and partly to adhering matrix; this has been removed, and the new figure (PI. XXVII, 

 fig. 1) shows all the essential characters very well for comparison with the more perfect 

 material now available. This consists of a series of excellent specimens from Nauvoo, 

 Niota, Keokuk, and Jersey County, Illinois. The fine specimen pictured in figure 3 was 

 found by the late Lisbon A. Cox, the veteran collector of Keokuk, to whose industry in that 

 field during 30 years we are indebted for by far the greatest collection of Keokuk crinoids 

 ever brought together. All the specimens are much flattened, and the true contours of the 

 crown are not shown by the figures. 



The specimen figured under this name by Meek and Worthen, in volume 5, Geol. Surv. 

 Illinois, plate 14, figure 2, is from the eastern Keokuk of Indiana at the typical locality of 

 F. multibrachiatus, and must be referred to that species. Forbcsiocrinus macadamsi of 

 Miller and Gurley, from Jersey County, Illinois, is a fine and characteristic example of the 

 present species; but their figure of it, Bulletin 9, Illinois State Museum, plate 5, figure 1, 

 is wholly incorrect as to the basal plates. Their F. jerscyensis, from the same locality, is 

 also a synonym. 



