218 



ECHINODERMATA— PELMATOZOA 



THYLUM IV 



Silurian and Devonian ; North America 

 Similar to Homocrinus, but with 



composed of numerous small plates. 



and Europe. 



Bactrocrinus Schnur, in Steininger. 



narrower facets. Devonian ; Germany. 



Euspirocrinus Angelin (Fig. 267). Dorsal cup conical. EA small, pent- 



agonal. Anal x rising above level of BB, with a plate of the anal tube 



partly in the cup beside it. Anus at the end of a strong tube. Arms 



dichotomous, branching. Ordovician ; Canada. Silurian ; Gotland. 



Closterocrinus and Ampheristocrinus Hall. Imperfectly known. Silurian ; 



North America. 



Sphaerocrinus Roemer. Dorsal cup globose. BA larger ; x not rising 



above BB. Anus directly through the tegmen. Axial canal separate from 



ventral groove in radials and brachials. Arms 

 unknown. Devonian ; Germany and England. 



Parisocrinus W. and Sp. (Fig. 315, which is 

 reversed). Dorsal cup elongate. BA large ; x not 

 rising above level of BB. Anal tube very broad 

 and long, rising to height of the arms, composed 

 of hexagonal plates and profusely perforated with 

 pores at the sides of the plates ; anus at the distal 

 end, surrounded by a circlet of strong plates. 

 Arms dichotomous, branching frequently. Devon- 

 ian to Lower Carboniferous (Keokuk) ; Germany, 

 England and North America. 



from the anal side, showing ventral Vasocfinus Lyou. Calyx broad, hemispherical. 



sac and one arm which is recuper- . t_ - ^ -j.!. x • • r, • 



ated and abnormaiiy small (right Arms heterotomous, With teu mam rami bearmg 

 '^.^^^:^S^tS^^i^^. strong ramules which may brauch again ; therami 



divergent, and not in contact above the axillary 

 Anal tube broad below, rather short and tapering. 

 not divided, and with very small axial canal. 

 Devonian to Lower Carboniferous (Keokuk) ; North America. 



Barycrinus Wachsmuth. Calyx and arms as in Vasocrinus, but rami and 

 ramules usually heavier. Rami in contact by one or two brachials above the 

 axillary. BA small, quadrangular, frequently entirely wanting, in which 

 case a small specimen cannot certainly be distinguished from Cyathocrinus by 

 the calyx alone, although in general the arm facets are larger, and directed 

 upward more than in that genus. Anal tube broad and short. Stem un- 

 usually large, quinquepartite, with a very wide axial canal. Specimens 

 attaining a large size. Lower Carboniferous (Lower Burlington to Warsaw) ; 

 Mississippian area. North America. 



Goniacrinus Miller and Gurley. Calyx small, elongate. Arms hetero- 

 tomous, with small ramules borne on ten main branches ; facets directed 

 upward. BA small. Anal x in line with radials, followed by others in a 

 prominent series between the posterior rays, passing into a tube. Lower 

 Carboniferous ; North America. 



Atelestocrinus W. and Sp. Calyx elongate. Arms heterotomous, with 

 delicate ramules. BA of good size. Anterior ray is not arm-bearing. 

 Lower Carboniferous (Burlington) ; Mississippian area. North America. 



Fig. 315. 



Parisocrinus eurtus Müll 

 ian ; Schönecken, Eifel. 



Devon - 

 a, Calyx 



primibrach. BA small. 

 Stem of moderate size, 



