CLASS III 



CRINOIDEA 



219 



Fig. 316. 



Gasterocoma antiqna Goldf. Devonian ; Priini, 

 Eifel. a, Calyx seen from one side ; h, Anal aspect ; 

 c, Tegraen. ^/i (after L. Scluiltze). 



Subfamily B. Gasterocominae. 



Ci/athocrinidae with no radianal. Anus through the dorsal cup, below level of 

 arm bases. Arms strong, round; facet horse-shoe shaped, directed outward, and 

 pierced by a distinct axial canal. Infrabasals usually undivided, exceptionally three 

 or five. Orals largely covered by modified ambidacrals ; posterior one a madreporite. 

 Stem round, with central axial caned surrounded by three or more peripheral canals. 



A strongly specialised subfamily of short life, being limited, except for 

 Hypocrinus, to the Middle Devonian. 



Gasterocoma Goldfuss {Epactocrinus and Ceramocrimis Joh. Midler) (Fig. 

 316). Infrabasal disk small, undivided. Anal opening lateral through the 

 dorsal cup, just above the posterior 

 basal, at the angle formed by that 

 plate and the two posterior radials, 

 usually fringed with a ring of small 

 plates ; one or more plates may lie 

 above it, connecting with the tegmen, 

 or these may be absent, leaving the 

 radials closely abutting. Axial open- 

 ing in infrabasal disk complex, consist- 

 ing of a central and three, four or five 

 peripheral canals, continued down into 

 the column. Stem round, with strongly alternating joints, the thin proximal 

 columnal more or less quadrangular. Arms not certainly known, but 

 divergent, directed outward, probably round and simple, with short brachials. 

 Middle Devonian ; Eifel: The remaining genera mostly agree with this in 

 the essential structures of the calyx. 



Schultzicrinus Springer. Arms directed upward, simple, broad, abutting, 

 with long brachials following one very short primibrach. Devonian 

 (Onondaga) ; New York. 



Arachnocrinus Meek and Worthen. Arms branching more than once. 

 Devonian (Onondaga) ; New York and Kentucky. 



Nanocrinus Joh. Miiller. Only four arm-bearing radials. Arms unknown. 

 Scoliocrinus Jaekel. Three arm-bearing radials. Middle Devonian ; Eifel. 



Achradocrinus Schultze. Infrabasals five, not fused. Axial canal simple, 

 without peripherals. Middle Devonian ; Eifel. 



Hypocrinus Beyrich may belong here. Resembling Achradocrinus, but 

 with three infrabasals. Classed by authors as a Cystid. Permian ; Timor. 



Myrtillocrinus Sandb. Has the general facies of this family ; undivided 

 infrabasal disk, a central axial with three or four peripheral canals ; round, 

 simple arms. But there are five large symmetrical orals in a pyramid con- 

 stituting almost the entire tegmen, leaving only small interoral grooves for 

 the ambulacra, — not preserved in any specimens. Anal opening not known, 

 probably minute, and obliterated by infiltration of calcareous matter in 

 fossilising. Middle Devonian ; Eifel and New York. 



Subfamily C. Cyathocrininae. 



Cyathocrinidae ivith no radianal. Anus at the ventral side, usually at the end 

 of a strong tube. Anal x, when present, in line with radials. Arms usually 



