TAXOCRINIDAE 437 



Onychocrinus pulaskiensis Miller and Gurley 

 Plates LXXIV, figs, i-io; LXXV, figs. 15a, b 



Onychocrinus pulaskiensis Miller and Gurley, Bull. 6, Illinois St. Mus. Nat. Hist, 1895, p. 40, pi. 4, 



figs. 1, 2. 

 Perhaps Onychocrinus parvus Miller and Gurley, Bull. 3, Illinois St. Mus. Nat. Hist., 1894, p. 52, pi. 4, 



fig. 5 (Insufficiently known for identification). 



A large species, of the type of O. ramulosus; but with more divergent 

 arms, shorter intervals between ramules, ramules at a greater angle with the 

 rami, and not connected with them by interbrachials. Rays deeply rounded; 

 brachials relatively not so short and wide as in ramulosus. IBr 3; IIBr to 

 first ramule 3 and 2. Ramules making a wide angle with rami, given off at 

 intervals of 2 and 3 ; not forming clusters, but branching again at short inter- 

 vals. Axillaries nodose. iBr, one large in the primary axil, followed by 

 perisome; none in higher axils. Column thicker than in any of the other 

 species, with convex and projecting nodal columnals. Average dimensions of 

 2 large specimens: Ray below fork, 31 mm.; ramus above fork, 63 (cannot be 

 traced to end) ; diameter of calyx, 30 mm. ; of base, 12. Number of clusters of 

 ramules, 10 or more. 



While this species in its chief essentials is clearly of the ramulosus type, the rounded 

 divergent rami and ramules, with the latter standing almost at right angles to the main 

 ramus, give to it a physiognomy quite distinct. Its one large interbrachial plate is more 

 like that of 0. distensus, which has a tendency toward some of its other characters. As the 

 latest known American species of the genus, it exhibits in its short intervals between ramules 

 the same tendency found in the accompanying Kaskaskia species of Taxocrinus. While 

 not so constant as in T. zvhitfieldi, the bifurcation on the second brachial occurs with con- 

 siderable frequency, sometimes in the IIBr, but more often higher up. Among a series of a 

 dozen specimens it appears more or less in all ; and it gives to the rays a zig-zag aspect which 

 is heightened by the sharp nodes upon the axillaries. On well-preserved specimens these 

 nodes are prominent, but on those that have been weathered, like the type and the large 

 figure 2, they are not so plain. 



The species is definitely characteristic for its horizon, and is well distributed. The best 

 locality for it is in Pulaski County, Kentucky, but I have it also from Grayson and Breckin- 

 ridge counties in that state, from Huntsville, Alabama, and from near Chester, Illinois. 

 Its stratigraphic position is in the upper beds of the Kaskaskia Group, now called the Okaw 

 formation. 



No other species has been described from this horizon except 0. parvus of Miller and 

 Gurley, founded upon a single extremely young individual which is probably of this species 

 (PI. LXXIV, fig. 8). The authors did not attempt any comparison with other species, say- 

 ing, — " This species is so much smaller than any other heretofore described that no com- 

 parison with any of them is necessary to distinguish it." My own numerous illustrations 

 of the young stages of various species of Onychocrinus show how uncharacteristic they are ; 

 and there is nothing in the figure or description of this one by which it would be possible to 

 identify a mature specimen, save only the possession of 3 IBr. Therefore,- although the first 

 described, I prefer to treat it as insufficiently defined, and to let this well-marked and dis- 

 tinctive species take the name of the later species, O. pulaskiensis, by the same authors. Their 

 description throws but little light upon its real characters ; but the type specimen, from the 



