208 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



Family 2. Pisocrinidae Angelin. 



Monocydk. Basais three to five ; radials five, very unequal, the riglit posterior 

 and right anterior Compound, left posterior and anterior usually 

 much the largest. Arms simple, uniserial and composed of long, 

 Silurian and Devonian. 



Fisocrinus de Kon. (Fig. 309, A). Calyx small, globose. 

 B five, unequal, forming a triangle. Only the large an- 

 terior, and the left posterior radial resting upon the 

 basals ; one large plate, the radianal, serves as inferradial 

 for both right posterior and right anterior radials, and 

 also meets the basals. Anal or first tube-plate above line 

 of radials, foUowed by a tube. Articular facets of the 

 radials impressed between vertical partitions formed by 

 the lateral margins of the plates. Tegmen rarely pre- 

 served, but as observed by Wachsmuth and Springer in 

 P. pilula, consisting of five large symmetrica! orals, above 

 which rises a narrow anal tube. Arms long, and com- 

 posed of extremely elongate, cylindrical ossicles. Silurian ; 

 Gotland, Dudley, England and North America (Niagara 

 Group). 



Triacrinus Münst. (Fig. 309, B). DifFers from the pre- 

 ceding in having but three B. Wachsmuth and Springer 

 have shown, however, that some of the Eifel specimens 

 occasionally have five B, thus leading to the inference that 

 the two forms are identical. Middle Devonian ; Eifel. 



Calycanthocrinus Follmann. B three. Additional small 

 arm-bearing plates introduced between the radials. Lower 

 Devonian ; Germany. 



Hypsocrinus Springer and Slocum. Calyx elongate. 

 Arm facets wide, shallow, concave, Alling a greater 

 part of radial margin. 



Fig. 309. 



A, Pisocrinus flagellifer 

 Ang. Silurian ; Gotland. 

 a, Perfect specimen, r. 

 posterior view ; b, Calyx 

 Seen from r. ant. side ; c, 

 From below. J/x (after 

 Angelin). B, Triacrinus 

 altus Müll. Devonian ; ß five 

 Gerolstein, Eifel. a 

 Calyx Seen from r. post 

 side ; b, From below i/i. -r> , t i i 



K. ant. radial has in- 

 ferradial distinct from radianal. Middle 

 Devonian ; North America. 



Family 3. Haplocrinidae Koemer. 



MonocycUc. Calyx small, pyriform to 

 Basals five. Three of the radials 

 Compound, the others, left posterior and an- 

 terior, simple, and much the largest. Orals 

 large, triangulär to pentagonal, laterally in 

 contact. Arms five. Devonian. 



Haplocrinus Steining. (Fig. 310). 

 Arm facets narrow, indented upon distal 

 face of radials. Arms small, simple, 

 uniserial, resting within deep grooves formed along the sides of the orals 

 Orals large, pentagonal, and laterally in contact ; the posterior one inter 



H>^a 



Fig. 310. 



Haplocrirms inesjnliformis Goldf. Devonian ; 

 Gerolstein, Eifel. a, Calyx seen from one side ; 

 fo, öeen from above ; c, Seen from below ; d, Analysis 

 of calyx ; h, Basals ; x, the three unsymmetrical 

 plates situated between basals and radials ; r, 

 Radials ; br, First arm-ossicle ; o, Orals (anterior 

 side to the right). 



