160 ECHINODERMATA PELMATOZOA SUB-KINGDOM in 



those of the It. 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. 



Woodocrinus, de Kon. and le Hon (Phttocrinus, de Kon. ; Pachylocrinus, "VV. and 

 Sp.), (Fig. 265). Dorsal cup saucer-shaped. IB five, small, generally 

 covered completely by the column. B large, their lower portions curving 

 inward together with the IB, 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 Woodocrinus 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 B. 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 ; IB 

 very small, generally covered by the column. Graphiocrinus 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 G-urley describe under Aesiocrinus 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, Trantsch. ; Eupachy- 

 crinus and Erisocrinus, M. and W. ; Geriocrinus, White ; and Ulocrinus, Miller and 



