THYSANOCEINID^ W, and Sr 



(GLYPTASTERID^ W. and Sp. 1885). 

 DiCYCLic. Lower brachials and interbrachials forming an important part of 



THE DORSAL CUP ; INTERBRACHIALS WELL DEFINED. RaDIALS IN CONTACT EXCEPT 

 at THE POSTERIOR SIDE, WHERE THEY ARE SEPARATED BY AN ANAL PLATE. 



Analysis of the Genera. 

 Infrabasals 5. 



A. Anal side slightly elevated. Anus without a tube. 



1. First anal plate followed by three plates. 

 J a. Dorsal cup deep. 



Arms uniserial, 10 PTYCHOCRmus. 



Arms biserial, erect, ten to twenty Thysanocrinus. 



b. Dorsal cup short., almost flat. 



Arms pendent, posterior oral and radial dome plates 



spiniferous Hyptiocrinus. 



2. All interbrachial spaces having a single large plate .... Idiockinus. 



B. Anal side bulging. Anus at the end of a tube. 



1. First anal plate followed by three small plates. 



Rays produced into tubular extensions. 



Infrabasals large Lampterocrinus. 



2. First anal plate followed by three large plates. 



Rays branching in the regular way. 



Infrabasals small . Siphonocrinus. 



Geological and Geographical Distribution. 

 Number of known species. 



(Open figures indicate American, those marked ( ), European.) 



Eormation. 



Thysanocrinid^. 



• 



General. 



American. 



Approximate 



European 

 Equivalents. 



1 



CO 



PI 



§ 



m 



CO 



o 

 O 



CO 



1 



CO 



pi 



I 



r-t 

 1 



CO 



• 1— 1 

 f-l 



o 

 o 



O 



■s 



■< 



M 



M 

 U 



M 



CO 



/ Upper 

 ( Lower 



Niagara. 



Dudley 

 Gotland. 





5(7) 



1 



4 



1 



3 



Huds. Eiver. 





2 













Total species ... 23 



2 5(7) 



1 



4 



1 



3 



