146 



ECHIXODERMATA PELMATOZOA 



SUB-KINGDOM III 



Cumberl. (Gilbertsowinus, Phill. ; Goniasteroidocrinus, Lyon and 

 Gassed.) Agreeing with Rhodocrinus in the structure of the calyx below the 

 arms, but readily distinguished by the so-called pseudobrachial appendages, 



and by the size and disposi- 

 tion of the arms. Above 

 each distichal is a round 

 ambulacra! opening (ten in 

 all), through which the am- 

 bulacra of the arms conduct 

 into the calyx. From above 

 each of these openings spring 

 two tufts of small, branching, 

 pinnule-bearing arms. These 

 are either folded over the 

 tegmen, or they bend down- 

 wards with the ventral side 

 exposed to view, the pinnules 

 being directed upwards. Ten 

 tubular appendages extend 

 outwards and downwards 

 from the upper margin of 

 the calyx. In the American 

 species these are united later- 

 ally in pairs for some dis- 

 tance ; but in the European 

 ones they are separated. One species in the Hamilton Group of New York ; 

 the remainder Sub-Carboniferous ; North America and Europe. 



Lyriocrinus, Hall. Calyx depressed ; plates smooth or finely granulose. 

 Tegmen almost flat, composed of a large number of small plates. Anus 

 eccentric; not extended in an anal tube. Arms ten, strong, simple, biserial. 

 Confined to the Niagara Group of North America. 



Rhipidocrinus, Beyrich (Fig. 248). Calyx cup- or urn-shaped, with a more 

 or less flattened or concave base. Plates of the dorsal cup heavy, and highly 

 ornamented. IB five, small, forming a pentagon. B five, equal ; R and 

 axillary costals pentagonal. First IR large, heptagonal. Tegmen low, com- 

 posed of an immense number of small thick plates, irregular in their arrange- 

 ment ; anus eccentric. Arms given off from calycular appendages, and 

 composed of wide transverse pieces, which bear at intervals on alternate sides 

 biserial, pinnule-bearing armlets. Column round, heavy ; axial canal pentalo- 

 bate. R. crenatus, Goldf. sp. Middle Devonian ; Eifel. 



Thylacocrinus, Oehlert. Resembling Lyriocrinus, but the calyx more elongate. 

 IR and interdistichals profusely developed. Arms numerous, heavy, biserial, 

 not branching in the free state. Devonian ; France and North America. 

 Dumenocriwus, Oehlert. Devonian ; Manche (France) and Germany. 



FIG. 248. 



]Hi!jiiilui 'riiius crenutus, Goldf. sp. Devonian; Gerolstein, Eifel. 

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

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

 II'.. two of the L', and one R. I), Column. E, Face of stein-joint. 



Family 8. Melocrinidae. Zittel (emend. W. and Sp.) 



Base monocydic. Basals three to five ; radials laterally in contact, not 

 an anal plate. Interbrachials frequently separated ly supplementary amis. Ordo- 

 vician to Devonian. 



