160 ECHINODERMATA—PELMATOZOA SUB-KINGDOM III 
those of the #. Arms long, uniserial, branching, and composed of wedge- 
shaped joints, alternately arranged. Sub-Carboniferous and Coal Measures. 
Scytalocrinus, W. and Sp. Dorsal cup generally deep. Arrangement of 
calyx plates as in the preceding, from which it differs in the character of the 
arms. These are stronger, and remain undivided after the first bifurcation, 
which takes place above the first or second brachial. They are straight, and 
composed of moderately short, very slightly wedge-shaped joints. Pinnules 
long and rather closely abutting. Sub-Carboniferous. 
Decadocrinus, W. and Sp. Dorsal cup very short, concave at the bottom. 
Arrangement of plates of the dorsal cup as in the preceding, but the arms 
simple and thinner, and composed of long, decidedly cuneate joints, which 
give them a strongly waving or zigzag outline. Pinnules very robust, 
closely resembling armlets, and widely separated. Sub-Carboniferous ; North 
America. 
W oodocrinus, de Kon. and le Hon (Philocrinus, de Kon.; Pachylocrinus, W. and 
Sp.), (Fig. 265). Dorsal cup saucer-shaped. JB five, small, generally 
covered completely by the column. J large, their lower portions curving 
inward together with the Jb, and forming a concavity. Anal area and mode 
of articulation as in Scaphiocrinus. Ventral sac short, bulging toward the 
upper end. Arms twenty or more, uniserial, heavy, and closely folded so 
as to be laterally in contact; arm-ossicles very short. Pinnules long and 
numerous. Column round. Sub-Carboniferous ; England and North America. 
Zeacrinus, Hall (Troost). Resembling /Wcodocrinus in form and construc- 
tion of the dorsal cup, but with short, thick, sub-pyramidal ventral sac. 
IRA and RA both present; the latter especially large, and deeply inserted 
between the 6. Arms short, uniserial; the two main divisions of each ray 
giving off numerous branches toward the inner side. These branches fit so 
closely together that when the arms are closed the crown appears like a 
perfectly solid body. Arm-ossicles short, transversely arranged. Middle 
and Upper Sub-Carboniferous. 
Coeliocrinus, White, and Hydreionocrinus, de Kon., are closely related to 
Woodocrinus and Zeacrinus. ‘They are distinguished chiefly by the form of the 
ventral sac, which in Coeliocrinus is balloon-shaped, and in Hydreionocrinus mush- 
room-shaped. They are found in the Lower and Upper Sub-Carboniferous 
respectively. 
Graphiocrinus, de Kon. and le Hon (Fig. 266), and Bursacrinus, M. and 
W., differ from the majority of the Poteriocrinidae in having but one anal 
plate, RA being absent. Dorsal’ cup depressed, concave at the bottom; JB 
very small, generally covered by the column. Graphiocrinis has ten main 
arms, which are simple; and the ten main arms of Bursacrinus give off 
branches in a similar fashion as in Zeacrinus. Sub-Carboniferous ; North 
America. 
Miller and Gurley describe under desiocrinus a Carboniferous form agree- 
ing with Graphiocrinus in the construction of the calyx; but the plates of the 
ventral sac are extremely heavy, and enclose a narrow cavity; while the 
plates of the sac in the typical form are rather delicate, and the inner space 
is relatively wider. 
[In addition to the above, the following genera have also been associated with the 
Poteriocrinidae :—Cromyocrinus, Phialocrinus, and Stemmatocrinus, Trautsch, ; Hupachy- 
crinus and Hrisocrinus, M. and W.; Certocrinus, White ; and Ulocrinus, Miller and 
