406 SMITHSONIAN INSTITUTION 



Taxocrinus shumardianus (Hall) 

 Plate LIX, figs. 13-16 



Forbcsiocrinus shumardianus Hall, Geology Iowa, I, pt. 2, 1858, p. 671, pi. 17, fig. I. — Meek and Worthen, 



Proc. Acad. Nat. Sci. Philadelphia, 1865, p. 140. 

 Taxocrinus shumardianus, Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, p. 49. — Keyes, 



Geol. Surv. Missouri, IV, 1894, p. 224. — Springer, Jour. Geology, XIV, 1906, pi. 7, fig. 17. 



A larger species than T. giddingei; similar to it in general aspect, form 

 and proportions, but differing in the fact that the basals in the regular areas 

 as well as in the anal are truncate and pass up between the radials to a sutural 

 connection with the first interbrachial ; they are therefore much more elongate. 

 Also the anal tube is smaller, and is bordered by the usual weak perisome of 

 the genus, instead of by strong plates at either side. The crown is usually a 

 little higher than wide, the average dimensions of 6 mature specimens from 

 the type locality being, — height of crown, 25 mm. ; width at level of first IIIBr, 

 23 mm. ; base, 5 mm. ; calyx, 10 mm. high at I Ax by 15 wide. 



While some specimens of smaller size occur at St. Louis, the type locality, the usual 

 habitus is like that of the type, figure 13 ; allowing for the smaller ones, the species averages 

 decidedly larger than the closely related form from Huntsville. The largest of all is the 

 beautifully preserved and very mature specimen shown in figures 14a, b, which was imbedded 

 in a very fine-grained calcareous matrix, from which I was able to free it on both sides. It is 

 the second Taxocrinus found preserving any recognizable portion of the tegmen. Here we 

 have some indistinct remains of the integument composed of extremely fine plates, part of 

 an ambulacrum, and the five orals lying near the center, but somewhat separated ; all these 

 have fallen down into the bottom of the calyx, and are therefore displaced. 



This crinoid must have been in a very unusual state of perturbation at the time of its 

 demise. Ordinarily the arms at death both in Recent and Fossil crinoids are found either 

 flexed or extended uniformly ; but in this case part are bent one way and part another, as may 

 be readily seen by comparing the two figures, in drawing which the specimen was rotated 

 sidewise so that left and right are reversed, the corresponding arms being lettered. In the 

 anterior ray, two of the arms at e are seen in the dorsal view (fig. 14a) to be folded back- 

 ward upon themselves, exposing their ventral side to the extremities, and those at / were so, 

 but are broken off ; the other view (fig. 14&) shows several arms (a'; b', c', d', g', h') curved 

 upon themselves in exactly the opposite way, the dorsal side of the distal extremities coming 

 into view as they bend over toward the disk. An interesting thing in this specimen is the 

 great thickness of the intersecundibrachs between the main divisions of the rays, which 

 project upon the ventral side like short pegs, being in this respect entirely unlike those form- 

 ing part of the calyx wall between the rays ; the smaller plates between the IIIBr project in a 

 similar way. 



The number of IIBr seems to be fixed at 3, with occasionally one wanting. And the 

 inner ramus of the IIIBr has almost uniformly only 3 plates, while in T. giddingei this is 

 only occasional. The fact that the interbrachials pass down to the basals is very unusual, and 

 constitutes an exceptional feature among the Flexibilia ; it occurs sporadically in Wachs- 

 muthicrinus thiemei, and occasionally in the next following species of the Kaskaskia ; but 

 nowhere else that I know of in this group. 



Types. Hall's original is in the Worthen collection, University of Illinois. The other 

 specimens figured and studied are in the author's collection. 



Horizon and locality. Lower Carboniferous, St. Louis Group ; St. Louis, Missouri, 

 perhaps passing up to the Lower Kaskaskia in Monroe County, Illinois. 



