152 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



Family 1. Echinosphaeritidae Neiimayr. 



Calyx glohular or bursiforni, adherent or with short stem, and composed of 

 7mmerous, irregularly arranged plates, all of which are furnished with pore-rhojnhs. 

 Ämbulacral grooves short, unhranched ; arms two to five,free, biserial, rarely preserved. 

 Stem, when present, composed of several vertical series of alternately arranged plates. 

 Ordovician and Silurian. 



Fig. 238. 



Echinosphaerites aurantium (Hising). Ordovician (Vaginatenlvalk) ; Pulkowa, Russia. a, Summit view of 

 calyx ; h, Calyx seen from the anal side ; c, Mouth, arms, and covered ämbulacral grooves ; d, Calyx plates 

 enlarged, showing pore-rhombs (cf. Fig. 231). 



Echinosphaerites Wahlenb. (Crystallocystis, Citrocystis, Trinemacystis Haeckel) 

 (Fig. 238). Globose, non-pedunculate. Mouth central, ämbulacral grooves 

 short. Anal opening protected by a valvulär pyramid ; arms unknown. 

 Very abundant in the Ordovician of Kussia and Scandinavia. 

 E. aurantium (Hising). 



Arachnocystites Neumayi-. Like the preceding, except 

 that it has strong arms, usually three in number, which 

 sometimes attain a length of 10 cm. Stem tapering dis- 

 tally to a point. Ordovician ; Bohemia. A. infaustus 

 (Barr.). 



Caryocystites v. Buch (Amorphocystis Jaekel) (Fig. 239). 

 Calyx plates relatively large. Pore-rhombs on external 

 surface elevated, prominent. Stem wanting. Ordovician ; 

 Eussia, Scandinavia, England. C. granatum Wahlenb. 



Palaeocystites Billings. Calyx ovate or pyriform ; plates 

 numerous, and porif erous at the margins. Ordovician ; Canada. 

 Orocystites Barr. Ordovician ; Bohemia. Heliocrinus Eichwald. Ordo- 

 vician ; Eussia. Stichocystis Jaekel. Ordovician ; Europe. 



Fig. 239. 



Caryocijstiteis grana- 

 <ttm(Wahlb.) Ordovi- 

 cian ; Oeland. Plates 

 of the natural size 

 showing elevated 

 pore-rhombs. 



Family 2. Oaryocrinidae Bernard. 



Calyx composed of a moderate number of plates exhibiting a more or less definite 

 arrangement in cycles. Certain or all of the side plates with pore-rhombs ; those of 

 the ventral surface imperforate. Food-grooves primitively three, branching, and 

 leading to free arms in varying number. Stem constantly present, occasionally long. 

 Ordovician and Silurian. 



Hemicosmites v. Buch {Hexalacystis Haeckel). Calyx composed of four 

 basal plates, two zones containing six and nine lateral plates respectively, and 

 a circlet of six plates forming the ventral surface. The latter carries three 

 short ämbulacral grooves, at the ends of which are situated small articular 



