188 



ECHINODEEMATA— PELMATOZOA 



PHYLÜM IV 



Bliodocrinus. 



Fig. 285. 



Analysis of calyx (after W. 

 and Sp.). 



uniserial ; from ten to twenty, and branching further. Otherwise similar to 



Ärchaeocrinus. Ordovician ; North America and England. 



Archaeocrinus W. and Sp. Calyx obovate to hemispherical ; base usually 



concave or invaginate. IBB small. Brachials to at least second order in- 



corporated in the calyx. Arms biserial, usually ten at their origin and 



branching beyond. Anal interradius 

 slightly distinguished by an additional 

 plate in second ränge ; iBr numerous. 

 Anus without a tube. Ordovician; Canada 

 and Kentucky. 



Diabolocrinus W. and Sp. Calyx de- 

 pressed globose. Anus at end of a tube. 

 First regulär interbrachial frequently 

 surrounded by supplementary plates. 

 Ordovician ; Tennessee. 



Deocrinus and Hercocrinus Hudson. 

 Ordovician ; Canada. 



Bhodocrinus J . S. Miller {Acanthocrinus 

 Koemer) (Fig. 285). Calyx globose, 

 usually small and delicate, with concave 

 base, and constricted at the tegmen. 

 Arms becoming free at the distichals, and 

 branching ; biserial, either directly from 

 the calyx up, or only from the last bi- 



furcation. Anal side frequently, but not always, distinct from the regulär 



interbrachial areas, by interposition of an extra plate in the second ränge. 



Devonian to Lower Carbon- 4 ß 



iferous (Keokuk Gr.); North 



America, England, Belgium, 



Germany. 



Gilbert socrinus Phillips 



{Goniasteroidocrinus Lyon and 



Cass.; Ollacrinus Cumberland 



nomen nudum). Calyx below 



the arm-regions like that of 



Bhodocrinus, but usually 



larger, expanding at the 



tegmen instead of constrict- 



ing, and distinguished especi- 



ally by large tubulär ap- 



pendages extending outward 



and downward from the 



margin of the tegmen, and 



overhanging the arm bases. 



These appendages are f ormed 



of rows of cylindrical plates, 



pierced to their füll length 



by a central canal ; they are 



primarily ten in number, in some species free, and in some fused by their 



outer margins to those of adjacent rays. Arms small, delicate, biserial, given 



Fio. 286. 

 lihipidocrinus crenatus (Goldf.). Devonian ; Gerolstein, Eifel. 

 A, Perfect crown, of the natural size (after Schnitze). B, Tegmen, 

 with eccentric anus. C, Interior view of the base, showing the flve 

 IBB, two of the basals and one radial. D, Cohunn. E, Face of stem- 

 joint. 



