190 



ECHINODERMATA— PELMATOZOA 



PHYLUM IV 



also comparatively large. Arms uniserial, sometimes interlocking. Silurian ; 

 Europe and North America. 



Periglyptocrinus W. and Sp. Basais five. Arms biserial, dichotomous. 

 Ordovician (Trenton Gr.) ; Canada and Kentucky. 



Scyphocrinus Zenker. Basais four. Arms uniserial, dichotomising fre- 

 quently. Calyx very large and elongate. Symmetry of dorsal cup slightly 

 disturbed by anals which are interposed between the interbrachials. Brachials 

 to lower part of the third order incorporated in the calyx, the upper ones free. 

 Interbrachials very numerous. Stem attached to a large, hollow spheroid, 

 strengthened by internal septa, regarded as a float by Hall ( = Camarocrinus), 

 as a Cystid by Barrande ( = Loholithus). Silurian and Devonian ; Europe and 

 North America. 



Mariacrinus Hall (Zenkericrinus Waag. and Jahn). Basais four. Arms 

 uniserial, branching once or twice. In general aspect, construction of calyx, 

 and surface Ornament, resembling Glyjptocrinus. Silurian ; America, Europe. 



Melocrinus Goldf. (Ctenocrinus Bronn, Astrocrinus Conrad, Turbinocrinus 

 Troost, Castanocrinus Eoemer, Clonocrinus Ö^hlert, Promelocrinus Jaekel). 

 (Figs. 288, 289). Basais four; interbrachials numerous; those of the posterior 



interray enclosing one or more 

 supplementary anals. Anal aper- 

 ture eccentric, rarely extended in 

 a small tube. Rays produced into 

 two main uniserial rami, giving off 

 biserial, pinnule-bearing arms at 

 short intervals to the outside of 



Fig. 288. 



Melocrinus typus (Bronn). Uevoiiian (Spiriferen-Sandstein) ; 

 Dann, Bifel. B, Basais. C, Mould of stem-joints (the so- 

 called " Schranbensteine "). 



Fig. 289. 



Melocrinus. Analysis of calyx (after W. 

 and Sp.). 



the bifurcation ; the rami may be separate (Silurian species), or more or 

 less fused by their inner margins (Devonian species). Column roun(?r Silurian 

 and Devonian ; Gotland, England, Germany and North America. 



Cytocrinus Roemer. Like Melocrinus, but with arms borne on a single main 

 radial trunk from each ray. Silurian ; America. 



Clonocrinus Quenstedt. {non CEhlert ; Corymhocrinus Ang. ; Polypeltes Aug.). 

 Basais four, hidden by column. Arms dichotomous, biserial both above and 



