CARADOCIAN CYSTIDEA FROM GIRVAN. 499 



cystidae, Rhipidocystidae ?, Ceratocystidae, Cothurnocystidae, Trochocystidae, and 

 ADomalocystidae (§§ 18-32). 



The Family Dendrocystidae is rediagnosed (§ 38), In the genus Dendrocystis, 

 the genotype D. Sedgwicki Barr. is restricted and redescribed (§ 108) ; the specimens 

 from Trubsko, d2, previously included in it, are separated as a new species, D. Bar- 

 randei (§ 89) ; D. scotica is a new species from Girvan (§ 127) ; D. rossica Jaekel is 

 partly described (§ 150); and Syringocrinus paradoxica Billings is referred, with 

 very slight hesitation, to this genus (§§ 42, 155). 



The genus Rhipidocystis is briefly discussed, and thought to be synonymous with 

 Platycystites S. A. Miller. The need for a Family Rhipidocystidae is questioned 

 (§§ 34-37). 



The new Family Cothurnocystidae (§ 160) is established for the reception of the 

 new genus Cothurnocystis (§ 161), with its two species from Girvan, C. Elizas (§ 170) 

 and C. curvata (§ 208), of which the former is the genotype. 



§ 577. The Order Rhombifera is discussed and its content compared with that of 

 Jaekel's Order Dichoporita (§§ 261-264). Any attempt to split up the Rhombifera 

 into Suborders, such as Jaekel's Regularia and Irregularia, is dismissed as impractic- 

 able for the present (§§ 265, 266). The relationship of the genera formerly placed by 

 me in the Glyptocystidae and by Jaekel in the Regularia is, however, recognised by 

 assembling them in a Superfamily Glyptocystidea (§§ 267-282). This comprises the 

 Families Echinoencrinidae, Callocystidae, and Cheirocrinidae. A complete list of their 

 contained genera is given (§ 281). 



The Family Cheirocrinidae is diagnosed (§ 283), and taken to include Cheirocrinus 

 (? Homocystis), Glyptocystis, Pleurocystis, and Cystoblastus. The establishment of 

 a Subfamily for each of these may be logically correct, but meets no practical need 

 (§ 285). 



The genus Cheirocrinus receives a fresh diagnosis (§ 287), and the history of opinion 

 concerning it is summarised (§ 289). A list of species is given (§ 307). The species 

 found in Girvan are C. constrictus n. sp. (§ 310) and C interrwptus Jaekel (§ 336). 



The treatment of Pleurocystis only comes short of being monographic because the 

 time allowed me for the completion of this memoir was not enough to enable me to 

 study the actual type-specimens of the American species. The genus is diagnosed 

 (§ 349), its genotype is held to be P. squamosa (§ 350), and the history of opinion as 

 to its systematic position is summarised (§ 351), A redescription of the genus (§ 366) 

 forms a basis for an appreciation of the diagnostic characters of the species (§ 394). 

 The American species are then revised and rediagnosed, viz. P. squamosa Bill. 

 (§ 403) et var. rohusta Bill. (§ 408), P. Jilitexta Bill. (§ 414), P. elegans Bill. (§ 420), 

 P. exornata Bill. (§ 426), P. anticostensis Bill. (§ 432), and P. mercerensis Miller & 

 Gurley (§ 438). The British species are diagnosed and fully described; they are: 

 P. Rugeri Salter from Wales (§ 444), P. anglica Jaekel from Tyrone (§ 464), and the 

 following new species from Girvan, P. procera (§ 486), P. quadrata (§ 501), P. gibha 



