THYSANOCRINIDaE. 



189 



RemarJcs. — We have changed the name Gljptasteridge, which we pro- 

 posed in 1885,*' into Thysanocrinidse, because we found it necessary to give 

 up Hall's genus Glyptaster. "We also discard Dimerocrinus Phillips^ and Eu- 

 crinus Angelin, and arrange the species of both under Thi/sanocrinus.-\ That 

 Phillips' figures of Dimerocrinus were insufficient for generic identification, is 

 shown by the fact that the genus has been referred by Roemer and Dujardin 









xa 





Fig. 8. Thysanocrhius. 



Fig. 9. Lampterocrimis. 



and Hupe to the CyathocrinidaB, while Zittel made it the type of a mono- 

 cyclic family. Gly piaster ^ti^ Eucrinus were placed by Zittel along with 

 Lampterocrimis, Archceocrimis, and Glyptommis under the Glyptocrinidse ; in 

 which he was followed by S. A. Miller, who added Reteocrinus and Xenocrinus, 

 but withdrew them again in 1889. Thjsanocrmus was placed at first by both 

 authors under the Ehodocrinidse, from which afterwards Miller removed it to 

 the Glyptasteridse. 



The Thysanocrinidae have their closest affinities with the Ehodocrinidse. 

 Both are dicyclic, but in the RhodocrinidjB the interradials at all ^^^ sides 

 are in contact with the basals, thus, as a general rule, completely isolating 

 the radials laterally ; while in the Thysanocrinidse the radials are in contact 

 all around except at the posterior side, where the anal plate overlies the 

 basals. This bilateral symmetry in the arrangement of the plates of the 

 dorsal cup is accompanied by a marked asymmetry in the general form of 

 the calyx, and especially of the ventral disk, which is more or less enlarged 



* Revision, Part III., p. 89. 



t See under ThysanocrhiMs. 



