CARADOCIAN CYSTIDEA FROM GIRVAN. 451 



If, however, the genus is in itself homogeneous and unmistakable, its very pecu- 

 liarities have in the past caused much misconception as to its affinities. 



§ 352. E. Billings (1854, pp. 250, 274) could find no better genus than Hemi- 

 cosmites with which to compare his new fossil. 



§ 353. E. J. Chapman (1857, p. 303) placed Pleurocystis between Hemicosmites 

 and Callocystis. 



§ 354. E. Billings (1858, p. 47) considered that, in the arrangement of the antanal 

 thecal plates, Pleurocystis was " related to that group to which Echino-encririites 

 belongs ; while the ventral side ... is more like the body of a Sphaeronite." 



§ 355. J. Hall (1859, p. 152) placed Pleurocystis between Callocystis and 

 Malocystis, saying. " There appears to be some analogy between this genus and 

 Anomalocystites." 



§ 356. K. A. VON ZiTTEL (1879, p. 422) correctly placed this and other genera 

 bearing pectinirhombs in division c of his group Rhombiferi, comparing Pleurocystis 

 with Echinoencrinus. 



§ 357. R. HoERNES (1884, p. 124) placed the genus between Echinoencrinus and 

 Prunocystis, but, oddly enough, referred all three, not to the Lepadocrinidae, but to 

 the Caryocrinidae. 



§ 358. M. Neumayr (1889, p. 413) seems to have been the first to regard the peculiar 

 modifications of Pleurocystis as characterising a Family, " welche wir als die Pleuro- 

 cystiden bezeichnen." With it he associated Trochocystis, Ateleocystis, Bcdanocystis, 

 and Mitrocystis. 



§ 359. P. H. Carpenter (1891, p. 12) was the first to express clearly, if briefly, the 

 close relations of the genus to Cheirocrinus, though his identification of the individual 

 plates is not that now accepted. He wrote, " in the Russian Glyptocystis pennigera, 

 the anal opening is greatly extended at the expense of two basals (7, 8) and three 

 radials(l2, 13, 14), and was covered, according to Schmidt, by a delicate plated integu- 

 ment. From such a form as this the transition is easy to Pleurocystis, Billings, in which 

 basals 7 and 8 and radial 13 seem to be altogether lost in the integument of small 

 plates covering the anal side. Compare, for example, figs, la and \c on plate i., or 

 figs, la and \h on plate ii. of Billings's memoir, with figs. 7 a. and 7d on Schmidt's tab. i. 

 On the other hand, the numerous pore- rhombs of Glyptocystis are reduced to three in 

 Pleurocystis, which are situated respectively on plates 1-5, 13-14, and 11-12, the first 

 of which is, as we have seen, common to all this group of Cystids." 



§ 360. Unfortunately this important and suggestive paper of Carpenter's has been 

 persistently overlooked by foreign authors, and so we find F, Bernard (1893, p. 206) 

 including in a "Famille. — Pleurocystides," Trochocystis, Pleurocystis, and Dendrocystis. 



§ 361. Even von Zittel was beguiled from his original position, and in his " Grund- 

 ziige" (1895, p. 150) made the same collocations as Neumayr and Bernard, tacitly 

 pointing out, however, that they should have adopted the existing name " Anomalo- 

 cystidae, Woodw." This remained unaltered in Eastman's translation (1896, 1900). 



