148 



ECHINODERMATA PELMATOZOA 



SUB-KINGDOM III 



numerous, and enclosing supplementary anals, which sometimes form a con- 

 tinuous series. There are also numerous interdistichals, and frequently 

 interpalmars, which form conspicuous depressions between the arm-plates. 

 Tegmen low, composed of minute irregular pieces ; anus eccentric. Arms ten 

 to twenty, branching in the free state, long, slender, and 

 uniserial. Column round, or exceptionally pentangular. 

 Ordovician ; North America. 



Stelidiocrinus Ang. (Harmocrinus, Ang.) Form of dorsal 

 cup as in the preceding, but the IR fewer and much larger, 

 and plates generally without ornamentation. Plates of the 

 tegmen also comparatively large. Arms uniserial, sometimes 

 interlocking. Silurian ; Europe and North America. 



Macrostylocrinus, Hall. B three, unequal, Anal interradius 

 much wider than the others ; its first row of IR consisting of 

 FIG "50 two interbrachials separated by a supplementary anal. The 



Giyptocrinus deca- fi rs t row in the four other interrays consisting of a single 

 dactyius Hail. Ordo- interbrachial. Arms ten, simple, and biserial. Silurian: North 



vician (Hudson River 



Group) ; Cincinnati, America. 



Allocrinus, W. and Sp. B three,- unequal. Interbrachials 

 few, longitudinally arranged. Arms uniserial. Silurian ; North America. 



Dolatocrinus, Lyon (Cacabocrinus, Hall). Dorsal cup perfectly pentamer- 

 ous, cup -shaped or saucer -shaped. B primitively three, but completely 

 anchylosed in the adult. Costals two ; interbrachials few, the first ones 

 extremely large. Tegmen comparatively flat, and composed of rather large 

 plates, of which the orals form the summit. Anus at the end of a short tube. 

 Arms biserial ; generally branching. Devonian ; North 

 America. 



Stereocrinus, Barris. Like the preceding, but the 

 anchylosis of the B incomplete, and with only one costal. 

 Hamilton Group ; North America. 



Family 9. Calyptocrinidae. Angelin. 



Base monocydic. Lower brachials and interbrachials form- 

 ing an important part of the dorsal cup, which is perfectly penta- 

 merous. Plates of the calyx limited to a definite number. 

 Basals four radials five, in contact all around ; costals 2x5; 

 distichals two; and palmar s 2 x 10, of small size.. Arms 

 twenty, resting in compartments formed by partitions attached 

 to the tegmen. Silurian and Devonian. 



Eucalyptocrinus, Goldf. (Figs. 251, 252). Calyx with a 

 deep concavity at the lower end, the B forming the bottom, 

 and the R the sides of an inverted cup. Supplementary Eucaiyptocri 

 pieces of the calyx consisting of 1 x 2 interbrachials, and GoSd. sp 'crown l "with 

 one interdistichal ; the latter of the same form as the inter- ^'V^rlo Sow the 

 brachials, and nearly as large as the two upper ones niclies in which the y 

 combined. Tegmen elongate, its upper part extended 

 to form a tube. It is composed of five ranges of plates, of which the two 

 middle ones are the least regular in their arrangement, and the upper one 

 closes the centre. Attached to the outer walls of the tegmen, and extend- 



nusreyvlaris, 



