44 THE CEINOIDEA CAMERATA OF NORTH AMERICA. 



at the distal end, where they form a large root with hundreds of small, very 

 delicate branchlets. 



In Dichocrinus the distribution and length of the cirri are extremely vari- 

 able. In some species they only occur at the lower part of the stem, where 

 they are short and arranged far apart. In others they continue up to near 

 the calyx, and are quite long. The former is the case in D. inornatus, in 

 which they are singly arranged, and rather slender. In D. parvulus and 

 D. delicaiiis, however, they follow the whole length of the stem, and are 

 arranged in sets of two or more, which are so long that the tips of the upper 

 ones reach up to the arms. But the most remarkable cirri occur in the 

 Carboniferous Campiocriniis myelodmtylus (Plate LXXV. Figs. 1 and 2) and 

 C. cirrifer (Plate LXXVI. Figs. 13 a, h, c), in which they begin at a short 

 distance from the calyx. The stem, as usually found in these species, is 

 coiled around the crown ; the joints are circular at the top, but gradually 

 become crescent-shaped, the concave side of the crescent directed to the 

 inner side of the coil, and both its horns giving off extremely long cirri from 

 alternate sides. Very similar cirri occur in the Fistulate genus HerpetocrinuSy 

 from the Silurian of Europe. 



Glyptocrinus apparently had no cirri at all, not even at the distal end, 

 and the stem was probably attached like that of the Comatulse in their 

 larval state by means of a dorso-central, i. e., the enlarged terminal plate. 

 Rhodocrinus nanus and R. Kirlyi have a few scattered cirri at the lower end, 

 singly arranged. 



The cirri of the Inadunata, so far as observed, are not only more slender, 

 but were apparently more flexible than those of the Camerata, and they 

 pass up more frequently to the top of the stem. The latter is often the case 

 among the Poteriocrinidse, especially in Scaphiocrinus and Graphiocrinus, in 

 which the nodal joints have variously from one to five rather delicate cirri. 

 That these appendages were highly flexible is shown by the fact that they 

 bend in all directions, — some being straight, others curling, some directed 

 upward, others downward, — a feature very different from that shown in the 

 Platycrinidas, Actinocrinidae, and Batocrinidae. 



Belemnocrinus florifer has very long and slender interradially disposed 

 cirri, which extend to the full length of the stem. It has three or four from 

 each nodal joint, the upper ones directed upwards, and extending to half the 

 height of the arms. B. typus, on the contrary, has no cirri to a length of 

 ISJ cm., and the stem is circular instead of stellate. 



