72 The Ottawa Naturalist [October 



given rise to five biserial arms, in accordance with the theory 

 favored by Clark. At best Comarocystites could have given 

 rise to only two biserial arms. 



3. Biserial arms and brachiolar pinnules in Caryocrinites. 

 Caryocrinites (Plate IV) is anomalous in presenting brachio- 



liferous free arms in which the ossicles of both the brachioles 

 and of the arms are biserial in arrangement. It is anomalous 

 also in other respects. Successive ossicles on the same side of 

 the arm usually alternate strongly in size, the lower ossicle of 

 each successive pair being distinctly shorter, sometimes, in 

 fact, being reduced to a small, transversely cuneate remnant 

 along the inner half of the horizontal suture separating the 

 larger ossicles. When both of these successive ossicles are more 

 nearly of the same size, both are in contact with the base of the 

 same brachiole, the lower, shorter ossicle of each pair being in 

 contact with one of the series of ossicles forming the brachiole, 

 and the upper, longer ossicle of the same pair being in contact 

 with the other series of brachiolar ossicles. Hence, it is possible 

 to regard not only the arm of Caryocrinites as made up by 

 lateral junction of two uniserial arms, but, in a precisely similar 

 manner, the brachiole of Caryocrinites might be regarded as 

 built up by the lateral junction of two uniserial pinnules, the 

 supporting brachial ossicles of each of these theoretical uniserial 

 pinnules still remaining distinct. 



As a matter of fact, the brachioles of Caryocrinites may be 

 diagrammed also as uniserial forms, the ossicles alternating in 

 position from right to left, across the brachiole, the lowest 

 ossicle at the base being regarded as the first ossicle of the 

 brachiole. 



4. Biserial brachiolar pinnules in Stephanocrinus. 



Biserial pinnules are so anomalous among crinoids that in 

 the case of Stephanocrinus. the only crinoid known to possess 

 them, Wachsmuth and Springer identified them as pinnules. 

 (Revision of the Palaeocrinidea, III, sec. 2, 1886, pp. 283, 284, 

 292), stating: "that these appendages, although they are equally 

 thin and short, are not pinnules, is proved by the fact that all 

 are supported by a radial plate, instead of being distributed 

 separately along the sides of an ambulacrum." More recently 

 (Zittel, 1913, p. 207) Springer has described Stephanocrinus as 

 possessing "arms with one short biserial trunk to the ray, giving 

 off slender biserial, non-pinnulate side arms from the outer 

 shoulder of each brachial." 



Evidently, Stephanocrinus is as anomalous among crinoids 

 as Caryocrinites is among cystids. 



In presenting the preceding lines, there is no desire to 

 favor the view that the biserial arms of crinoids have originated 



