TAXOCRINIDAE 425 



In general aspect, especially when the rays are horizontally extended, this species super- 

 ficially resembles 0. asteriaeformis of the same horizon and locality, but the differences 

 between them are constant and decisive. O. asteriaeformis has almost without exception 

 only 3 primibrachs ; in 19 good specimens, having 68 rays preserved, only two rays have 

 more than 3 IBr; while in 17 specimens of 0. diversus, having 48 rays preserved, less than 

 4 IBr are found in only 8 rays. The species can be separated at once with a fragment show- 

 ing the terminal part of the ray, not only by the small and non-divergent rami in 0. asteriae- 

 formis, but by the succession of ramules, even if only the outer margin of the ramus can be 

 seen. In the latter, ramules will be found successively at intervals of 3 brachials (excep- 

 tionally 4) ; while in 0. diversus the interval at that side will be 6 brachials (the intermediate 

 ramule being on the opposite side), and the clusters of ramules will be very much larger and 

 fewer than in the former species, in which there are from 8 to 10 clusters, against a maximum 

 of 5 in this. Also O. diversus is much the larger species of the two. 



The species is quite rare. Although the 17 specimens in my own collection and that of 

 the Museum of Comparative Zoology form a good series for its study, these are substan- 

 tially all that have been found among the collections made at Burlington in fifty years. The 

 preservation of the specimens of the genus at this locality is not favorable for fine structural 

 details ; but these are amply supplied by the next species. I have figured the two types, one 

 of which, showing the ventral side with the distal ends of the infolding clusters of ramules, 

 has been further cleaned, exposing the posterior oral and some adjoining structures dis- 

 placed (PL LXV, fig. 2). The other one, giving the dorsal view (fig. 1), is a very mature 

 specimen, having all the IIBr interlocking in pairs. My figure shows some parts of rays 

 not seen in the original figure in the Illinois Report ; these were accidentally detached from 

 the specimen, then in a fragile condition, when that figure was drawn by Mr. Roetter. In 

 the fine specimen shown by figure 3 the clusters of ramules on the right posterior ray are 

 somewhat obscured by a hard matrix, and I have restored them from another specimen, in 

 which they are extremely well-preserved, and which shows the exact mode of branching. 

 This specimen is not symmetrically extended, the anterior and right anterior rays being fore- 

 shortened ; the latter is abnormal, having only 2 IBr. 



Types. Meek and Worthen's originals are in the Museum of Comparative Zoology, 

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



Horizon and locality. Lower Carboniferous, upper Burlington limestone; Burlington, 

 Iowa. 



Onychocrinus ulrichi Miller and Gurley 

 Plates XXI, fig. 5; LXVI, figs. 1-10; LXV II, figs. 1-10; LXVIII, figs. 1-6 



Onychocrinus ulrichi Miller and Gurley, Jour. Cincinnati Soc. Nat. Hist., XIII, 1890, p. 17, pi. 3, figs. 2, 3; 

 Descr. New Species Crinoidea, p. 17, pi. 3, figs. 2, 3 (author's ed.) ; Geol. Surv. Indiana, 16th Rep., 

 1890, p. 339, pi. 3, figs. 2, 3. — <Wachsmuth and Springer, N. A. Crinoidea Camerata, 1897, p. 123 ; 

 Springer, Jour. Geology, XIV, 1906, p. 469, pi. 4, figs. 1-5. 



Onychocrinus cantoncnsis Miller and Gurley, 16th Rep. Geol. Survi Indiana, 1890, p. 359, pi. 7, fig. 9. 



A large species of the type of 0. diversus, and representing it in the suc- 

 ceeding formation; differing from it only in minor details. It has a relatively 

 larger calyx; the rays are rather stouter and rami relatively longer, with 

 clusters of ramules more extensively developed, reaching the number of 7 or 9 

 in maximum specimens, against not over 5 in similar specimens of O. diversus. 

 The anal tube is stronger, the socket in post. B larger and subcentral, nearly 

 as wide as its distal edge; iBr more numerous and reaching higher up, even 

 sometimes to the IIBr. Comparison of the figures of mature specimens of 



