SAGENOCRINIDAE 25 1 



same height as in the anal area, and abo'ut one plate less in width at correspond- 

 ing levels; illBr areas similar and proportionally smaller. RR and IBr three 

 or four times as large as BB, and fairly uniform in width. Height of B to R 

 toIAx, 1:2.5:2.7. 



IBr 2; IIBr usually 3, exceptionally 4. All brachials below IVBr more 

 than half as high as wide. In a large specimen the height and width of the suc- 

 cessive plates are as follows: B, 3.5x9; R, 10.5x12; IBn, 9x12; IBr 2 , 

 10x14; IIBr, 8x10; IIIBr, 5x8; IVBr, 2x6; VBr, 2x6.5; VIBr, 1.5x4; 

 VIIBr, 1.2 x 1.5; thus while the lower and more distal brachials are nearly as 

 high as wide, the intermediate ones, about where the free arms commence, are 

 relatively much lower and wider. In another equally large specimen where the 

 full connection cannot be traced, there are arms toward the distal end with 

 brachials about 1 mm. high and wide, and 2 mm. deep. The number of brachials 

 of the successive orders in the ray follows a fairly definite rule for the two 

 branches of the dichotoms, viz. : IIBr usually 3; then 4 or 5 and 7 or 8 IIIBr, 

 the larger number at the outer side of the dichotom; 5 to 8 and 10 to 15 IVBr, 

 with the smaller number at the outside; 8 to 12 and 15 to 20 VBr, the smaller 

 number still at the outside. There are two or more bifurcations beyond this, 

 with arms tapering very gradually and becoming very deep. Column large, 

 tapering from the calyx; proximal columnal the same diameter as the infra- 

 basal ring, which is scarcely distinguishable from it, and usually, but not al- 

 ways, adhering when the stem is displaced; upper columnals extremely thin, 

 numbering 25 in the first 10 mm. diameter in about that distance, beyond which 

 the column becomes cylindrical ; there a slight alternation of thicker and thinner 

 columnals begins, gradually becoming more pronounced downward ; but at no 

 place are the ossicles very thick, and all are smooth and of even diameter. When 

 weathered they show strong crenulation at the ends of the radiating striae of the 

 joint faces. 



This species has always been esteemed by collectors the finest fossil in the Burlington 

 limestone, and with the possible exception of F. saffordi it is the largest crinoid known among 

 the Flexibilia. It is one of the rarer species, not over twenty-five specimens having been found 

 among all the collections, of which more than half are in the author's material. It is usually 

 found with the arms inrolled from the fourth to the fifth bifurcation, and in none of the 

 specimens are they extended to their full length, though probably nearly so in figure la, 

 Plate XXVI. The calyx may be considered to extend to about the third bifurcation, where 

 the interbrachials pass into the tegmen, and the arms as shown by that specimen are at least 

 once and a half as long. The brachial series are strongly and abruptly elevated above the 

 level of the interbrachial areas, and look like rough longitudinal ribs. This, with the strongly 

 convex, often nodose, plates, both brachial and interbrachial, and the unusual length of the 

 lower brachials, gives to this crinoid a very striking appearance by which it is easily recog- 

 nizable from imperfect fragments. There is a tendency to contraction at the upper limits of 

 the interbrachials where the arms become free. All the specimens are more or less flattened, 

 but the natural contour and proportions are correctly shown in the restoration (text-fig. 35), 

 made from careful measurements on several specimens of about the same size 

 17 



