452 DR F. A. BATHER. 



§ 362. Miller & Gurley (April 1895, p. 60) seem to have been the first to use 

 the family name " Pleurocystidae," and this, they say, they do "provisionally, without 

 defining it, because this genus cannot belong to the Lepadocrinidae, where it has been 

 placed heretofore." 



§ 363. E. Haeckel (July 1896, p. 398) mentioned " Pleurocystida " as an alterna- 

 tive to " Anomocystida " ; but, later in the same year (" Amph. und Cyst.," p. 37), he 

 made the Pleurocystida, comprising Mitrocystis and Pleurocyatis, a Subfamily of the 

 Family Anomocystida [sic]. 



§ 364. 0. Jaekel (1899, p. 230), while recognising the relations of the genus to 

 Cheirocrinus, regarded it as entering on a new path of evolution, and therefore as 

 needing an independent Family, 



§ 365. K. A. V. Zittel, in the second edition of his " Grundzlige " (1903, p. 175), 

 adopted the Family "Pleurocystidae. Miller u. Gurley (emend. Jaekel)"; and this 

 has been followed in the third edition by F, Broili (1910, p. 187). 



§ 366. Description of the Genus. — The general structure of Pleurocystis is so well 

 known, thanks to the descriptions and figures by E. Billings, 0. Jaekel, and others, 

 that it is only necessary to discuss here a few of the more doubtful or ditiicult points. 



The plates of the Theca are so greatly modified that it is not easy to trace their 

 homologies. The first person to do this seems to have been P. H. Carpenter (1891, 

 p. 12) in the passage quoted above (§ 359). There is probably a slip in his statement 

 that a pectinirhomb is borne on plates 13-14, since a few lines before he regards plate 

 13 as lost among the periproctals ; the rhomb in question is 10-14. To the fate of 

 plate 13 we shall recur. Plates 7 and 8, however, are undoubtedly present, and can 

 only have escaped the notice of Carpenter if he based his remarks on Billings' figures 

 rather than on actual specimens. With these exceptions, I gather that Carpenter's 

 numbering of the plates would have agreed with that adopted by me (1900, p. 65), at 

 all events for the numbers up to 1 6. 



§367. The numbering of the plates on Prof. Jaekel's diagram (1899, pp. 195, 

 232; see our text-fig. 60) extends only to the equivalent of plate 14, and thus far 

 agrees with my numbering (1900). There is, however, a difi'erence in regard to plates 

 2 and 3, and the fact is that we were both wrong. He was more correct in showing 

 the relations of 3 and 4, and I was more correct in respect to 1 and 2. In our repre- 

 sentation of plates 15, 16, 17, 18, 20, and 23, we also agreed, but as regards the equi- 

 valents of plates 19, 21, 22, and 24, there were slight differences in our diagrams. It 

 is quite possible that these depended on individual differences in the specimens examined 

 by us. Both our diagrams were based on P. jiUtexta. 



§ 368. I have taken Prof. Jaekel's diagram as expressing his real views. Un- 

 fortunately it does not agree with the numbering on his plate-figures. Thus, in pi. 

 12, ff". 3, 4, 5, representing P. jiUtexta, and fi". 6, 6a, representing P. anglica, "6 1 " 

 is rightly placed beside plate 2, although in the diagram that plate forms part of 

 plate 1 [ = 6 2]. In pi. 12, "64" rightly denotes plate 3, which in the diagram is 



