LECANOCRINIDAE I4 1 



height to width at top of RR, about i to 1.7; crown probably constricted above 

 radials, and short. Base broadly rounded, and usually shallowly concave. Sur- 

 face, unknown, but plates marked by strong ridges radiating from a central node 

 and passing from plate to plate. Complete crown unknown. Maximum speci- 

 men, 17 mm. high by 25 mm. wide at top of RR; average specimen about 10 by 

 17 mm. ; width of base at lowest curve of basals in large specimen 10 mm. 



IBB large, restricted to the basal concavity, and not visible in side view. 

 BB very large, curving upward and occupying two-thirds the height of the 

 calyx. RA small. Anal x low, as wide as high, not rising above level of radials. 

 RR small, not over two-thirds as high as the basals; height of B to R to IBr, 

 8:5:2. IBr 2; these and succeeding brachials short and wide, unknown above 

 lower IIBr. Column unknown. 



This species is only known from internal casts found in the Magnesian limestone at 

 Chicago. The form of the calyx is wholly different from that of the typical Lecanocrinus, 

 its broad concave base and extremely large basals having no parallel except in part as to the 

 base in L. roenieri. Hall's type -specimen figured in the 20th Regent's Report, plate 11, 

 figures 11 and 12, shows a rather protuberant base, but this is not the usual habitus of the 

 fossil ; the base seems to be more often concave than flat. It is curious that the casts of this 

 species, occurring in the same matrix as Ichthyocrinus corbis, sometimes also show a distor- 

 tion of the lower part of the calyx, one side hanging lower than the other (PL III, fig. 23) ; 

 but this is by no means frequent. 



The strong radiating ridges mentioned by Hall are not confined to the " subradials " 

 (basals), but extend across the margins of those plates and concentrate again at the middle 

 of the radials, marking the course of the dorsal nerve cords. It is probable that these repre- 

 sent similar and perhaps stronger ridges on the outer surface of the plates, which is also a 

 feature not found in any other species. 



The small specimen figured by Weller under this species (op. cit., pi. 15, fig. 11) is a 

 different thing, and I have referred it to Pycnosaccus. 



Type. The original of Hall's figure in 20th Report, plate 11, figures 11 and 12, is not 

 claimed by either the American Museum or New York State Museum and its fate is unknown. 

 The specimens figured herein are in the author's collection, except figure 25 which is in the 

 Walker Museum, University of Chicago. 



Horizon and locality. Silurian, Racine dolomite formation of the Niagaran limestone 

 in the Chicago area ; Chicago, Romeo, Lemont and Joliet, Illinois. 



Lecanocrinus roemeri Schultze 

 Plate III, figs. 30-32 



Lecanocrinus Roemeri Schultze, Mon. Echinodermen Eider Kalkes, 1867, p. 41, pi. 3, figs. 8a-g. — 

 Beyrich, Monatsber. Akad. Wiss. Berlin, Feb., 1871, p. 46 (Transl. in Ann. and Mag. Nat. Hist., 

 (4) VII, p. 404. — Quenstedt, Petref. Deutschlands, IV, 1876, p. 516, pi. 108, fig. 27. — Wachsmuth 

 and Springer, Revision Palaeocrinoidea, pt. I, 1879, p. 40. — Springer, Jour. Geology, XIV, 1906, 

 p. 491. 



A large species. Crown subconical, truncate below, broadly expanding 

 from base, widest about IBn; average height to width at RR, I to 2.5, spread of 

 calyx to same height from 7 mm. at base to 22 mm. Side outline straight or 

 slightly convex; cross-section at IBr pentagonal; base small, sharply excavate. 

 Surface marked by small raised granules and wrinkles ; calyx walls moderately 



