TAXOCRINIDAE 435 



lateral ray unbranched ( fig. 1 1 ) , and the other with a sixth ray doubled and wedged into 

 the interbrachial area between the left posterior and left anterior rays (fig. 12). Lyon 

 recorded the species from Clear Creek, Hardin County, Kentucky ; but his description was 

 made upon a good series of specimens from Crawfordsville. I have reproduced his draw- 

 ing of the principal type specimen made for his monograph (PL LXXII, fig. 1). It does not 

 well represent the arcuate sutures, which are much more conspicuous in the specimen, but it 

 gives in general an excellent picture of the species. The specimen of figure 5 was among 

 some other crinoids known to be from Barren County, Kentucky, and there is no reason to 

 doubt its occurrence there, as the beds are typical Keokuk. 



Types. Author's collection. 



Horizon and locality. Lower Carboniferous, high in the Keokuk group; Crawfords- 

 ville, Indiana; Clear Creek, Hardin County, and Barren County, Kentucky. 



Onychocrinus magnus Worthen 

 Plate LXXIII, figs. 1-4 



Onychocrinus magnus Worthen, Geol. Surv. Illinois, VI, 1875, p. 520, pi. 31, fig. 5. — Wachsmuth and 

 Springer, Revision Palaeocrinoidea, pt. 1, 1879, p. 55. 



A robust form with massive main rays, intermediate in the principal char- 

 acters between the exsculptus and ramulosus groups. It has the distended 

 rami and small ramules of the former, with the few interbrachials in the main 

 axils and the greater relative length of rami of the latter. The single large 

 interbrachial is directly followed by plated perisome (PI. LXXIII, fig. 2a), 

 and this is probably the case in the higher axils, which have but one solid plate 

 instead of many as in ramulosus. The number of primibrachs is unstable, 

 being 3 or 4 in nearly equal proportions. Dimensions from average of 4 speci- 

 mens: Length of ray to fork, 21 mm.; of ramus above fork, 42 mm.; diameter 

 of calyx at IBr 3 , 28 mm. ; diameter of base, 9 mm. ; number of ramule clusters, 

 9 to 13. 



The type specimen is an unusually large and mature specimen ; as originally figured 

 in volume 6 of the Illinois Reports, plate 31, figure 5, it did not show any ramules, but with 

 the further preparation I have given it they are now plainly exposed (PL LXXIII, fig. 1). 

 This specimen has the arcuate sutures in profusion, the original surface having been pro- 

 tected by a fine clay matrix ; but the other specimens figured were in a hard limestone exposed 

 to weathering, by which the superficial curving of the sutures was to a large extent obliter- 

 ated (figs. 2<z-4). But figure 2b, from a ray not exposed to weathering, shows the sutures 

 as strongly curved as in the type. 



Type. In the Illinois State collection at Springfield. 



Horizon and locality. Lower Carboniferous, St. Louis group ; near Waterloo, Monroe 

 County, Illinois, and at St. Louis, Missouri. 



