258 SMITHSONIAN INSTITUTION 



other species, and the calyx is therefore relatively higher. The specimens are but little 

 distorted and exhibit nearly the natural contour ; the most perfect one, figures Ja, b, is some- 

 what compressed vertically. , 



Types. The original of figures 6a, b, is in the University of Chicago ; that of figures 

 Ja, b, in the author's collection. 



Horizon and locality. Lower Carboniferous, Keokuk Group ; Muldraugh Hill, Ken- 

 tucky, and White's Creek, Tennessee. 



Forbesiocrinus greenei Miller and Gurley 

 Plate XXX, figs. 1-2 



Forbesiocrinus greenei Miller and Gurley, Bull. 9, Illinois St. Mus., 1896, p. 57, pi. 4, figs. I, 2. 

 Proguettardicrinus ? greenei, Steinmann, Geol. Grundlagen der Abstammungslehre, 1908, p. 152, fig. 79. 



A large species. Crown low globose, wider than high, contracting rapidly 

 above IIIBr; greatest width at IIIBn, where height to width is 1 to 2.1; of 

 calyx at upper limit of iBr, 1 to 1.4; spread of calyx from column facet, 1 to 

 4.4; height to width of crown, 1 to 1.2 ; height of calyx to crown, 1 to 1.2. Cross- 

 section circular; side outline broadly curving. Base flush with top columnal. 

 iBr small, numerous; areas long and wide, not depressed; rays not prominent. 

 Calyx plates almost flat, and flush with the general curvature. Proportions of 

 plates in the brachial series different from those of preceding species, RR and 

 IBr being relatively shorter and wider, while IIBr and succeeding brachials 

 are longer and narrower. Dimensions in millimeters of successive plates in 

 characteristic specimens as follows: B, 4x9; R and IBri and IBr 2 , 4x11; 

 IBr 3 , 7x11; IIBr, 5x9; IIIBn, 5x7; IIIBr 6 , 2.5x5; the IIIBr therefore 

 diminish rapidly in width, thus leaving space for the extension of the iBr areas. 

 Post. B followed by a single anal plate; above it two or three, and then the plates 

 extend in ranges of four abreast to the height of IIIBr 2 or 3, and continue with 

 diminishing width beyond the next bifurcation. Regular iBr areas extend 

 above the highest IIIBr. Measurements of mature specimen: height of crown, 

 estimated from the curvature and taper of rays, 52 mm. ; calyx to top of iBr, 

 44 mm. ; width at IIIBri, 61 mm. ; base at column facet, 15 mm. Column large, 

 continuous with base, and tapering as in other species. 



The low, globose crown and flat plates distinguish the species readily from any other. 

 The zone of greatest width is much lower than in the last species, and the crown contracts 

 rapidly above that, as is indicated by the rapid tapering of the tertibrachs which in all the 

 preceding species remain about the same width ; this is partly compensated by the higher 

 limit of the interbrachials which extend beyond the line of preservation in either of our 

 specimens, and must have reached up between the quartibrachs. The species was described 

 from a single specimen, but its characters have since been confirmed by the discovery of 

 another one in better preservation from the same locality. Both are entirely rotund and 

 give a good idea of the natural contour, but neither has any of the free arms preserved. 

 The locality is in the extreme southern part of Indiana, and the horizon approximately the 

 same as that of the last species, both occurring high in the Keokuk Group next to, or perhaps a 

 part of, the Warsaw. 



