THE CYSTJDEA 



77 



Fio. XLVIII. 



Gomphocystis tenax, from above 

 showing course of food-grooves, 

 and from side with outlines of 

 plates shown only in upper part. 

 After Hall, x J. 



Gomphocystis, Hall (1864), Silurian, N. America 

 XLVIII.). Theca flattened above, greatly 

 elongate below, composed of many irregular 

 plates, pierced by diplopores. From a central 

 mouth five food -grooves radiate over the 

 theca, curving sinistrally around the upper 

 part, and occasionally descending a short dis- 

 tance on the stem-like base. Covering-plates 

 often strongly developed, and grooves lowered 

 beneath thecal surface. Jaekel (1895) states 

 that small side -grooves, but no brachioles, 

 occur in a Gotland species. Anus close to 

 mouth, in an interradius. Attachment ap- 

 pears to have been by the base, as in Aristo- 

 cystis. The curving of the food-grooves and the 

 asserted absence of brachioles cause Gompho- 

 cystis to resemble many Edrioasteroidea. But 

 the structure of the grooves seems to be that 

 which obtains in Diploporita, while the 

 presence of marked diplopores confirms the 

 reference to that order. In any case the family is out of the main line 

 of evolution. 



APPENDIX TO CYSTIDEA. 



The following names have been supposed to refer to Cystids : 

 Ascocystis, Barr. , probably a Camerate Crinoid. 

 Balanocystis, Barr., indeterminable. 

 Cainarocrinus, Hall (syn. Lobolithus, Barr.), root of a Crinoid (Scyphocrinus, 



apud Jaekel). 



Cardiocystis, Barr., indeterminable. 

 Crinocystis, Hall, probably a Camerate Crinoid. 

 Cydocrinus, Eichwald (Pasccolus, Billings), now regarded as calcareous Algae ; 



at any rate not Echinoderms. 

 Cystidea, a name used by Barrande for any indeterminable fragment, and not 



intended as a zoological genus. 

 Dictyocrinus, Conrad, is a Receptaculite. 

 Hyponome, Loveii, the ejected viscera and disc of an Antedon. 

 Hypocrinus, Beyrich, an Inadunatc Crinoid (see p. 178). 

 Lichenocrinus, Hall, the root of a Pelmatozoan (see p. 133). 

 Mespilocystis, Barr., probably Stephanocrinus (see p. 96). 

 Neocystis, Barr., probably the root of a Pelmatozoan. 

 Porocrinus, an Inadimate Crinoid (see p. 172). 

 Rhombifera mira, Barr., is a Stephanocrinus (see p. 96). 



A fairly complete Bibliography of the Cystidea was given in 

 Barrande, /., 1887. Systeme Silurien du centre de la Boheme, l re Partie : 

 Recherches Paleontologiques. Vol. VII. Classe des Echinodermes. Ordre 

 des Cystidees, 4to, xvii. and 232 pp., xxxix. pis. Prague. 

 The literature is so interwoven with that of Crinoidea and Blastoidea, that 

 other references are reserved for the list at the end of Pelmatozoa (p. 211). 



