V>KI>I:K irr 



r Kl NOI I )EA FISTULATA 



Gatteroooma antiqua, QolAt Devonian; Priim, 

 Eifel. o, Calyx seen from one side ; b, Anal aspect ; 

 < , .Teginen. /l (after L. Schultze). 



Family 7. Gasterocomidae. Warhsmnth and Springer. 



Base dic>/<-lir. fnfnilxixals anchylosed into an undivided disk, which is 

 by a hi nir </u<i>/riluhate canal. Radials large; articular facets directed outward, 

 horseshoe-sluiped, occupy i/i't //m/7// the whole outer face of the plates, and pierced //// " 

 large dorsal canal. Anal opening low down, situated directly above the anal plate and 

 fa-,, ,-,1,1'nih. Tegmen composed of five interradials, five orals, and ambulacral 

 plates. Devonian. 



Gasterocoma, Goldf. (Epactocrinus, Miiller), (Fig. 257). Irifrabasal disk 

 extending but slightly beyond the column ; surrounded by five B, of which 

 the posterior one is slightly truncated. 

 R five, three of them equal, the two 

 posterior ones irregular; the latter 

 enclose the IRA and anal opening, 

 which is surrounded by a few small 

 pieces. The arms, as indicated by the 

 character of the radial facets, either 

 recumbent or widely divergent. De- 

 vonian ; Eifel. 



Nanocrinus, Miiller. Similar to the 

 preceding, but only four of the R 

 arm -bearing. The right antero - lateral one, however, has two articular 

 facets, and evidently supported a pair of arms instead of a single one ; the 

 anterior R is considerably smaller, and has no articular facet. Devonian. 



Achradocrinus, Schultze ; Scoliocrinus, Jaekel. Devonian ; Germany. 



Family 8. Cyathocrinidae. Roemer (emend. Wachsmuth and Springer.) 



Base dicyclic. Radials simple or compound; their upper edges furnished with 

 a small crescent-shaped facet. Radials and arm-plates united by close suture, as are 

 the latter among each other. IRA usually, and RA occasionally present. Tegmen 

 with five orals and a madreporite, extended into a strong ventral tube. The disk 

 ambulacra resting on the lateral margins of two large interradial plates ; they are 

 lined by side-pieces, and roofed over with covering plates. Arms without pinnules, 

 long, branching, and uniserial. Ordovician to Carboniferous. 



Dendrocrimis, Hall (? Palaeocrinus, Billings). Calyx obconical, higher than 

 wide, unsymmetrical. IB five, equal. B five, the largest plates in the 

 calyx; the posterior one truncated at its upper face, and supporting a large 

 anal plate. Four of the R pentagonal and simple ; the right posterior one 

 compound, with the two parts vertically arranged. IRA succeeded by two 

 or three plates which form the base of the ventral sac, but are partly 

 enclosed in the calyx. Ventral sac very large. Arms long and branching ; 

 column sharply pentagonal, or sub-pentangular. A number of species occur 

 in the Ordovician of North America, but only a single doubtful one known 

 from the Silurian (Niagara Group). 



Homocrinus, Hall (Fig. 258). Like the preceding, except that the arm- 

 bearing portion of the right posterior radial is pushed over toward the right, 

 so as to support, conjointly with the anal, the ventral sac. Silurian ; North 

 America. Devonian ; Rhineland. 



Gastrocrinus arid Rhadinocrinus, Jaekel ; Bactrocrinus, Stein. Devonian. 



