498 DR F. A. BATHER. 



evidence for other openings in the theca is discussed and rejected (§ 76). The stern 

 is accurately described and its distal extremity made known (§§ 81, 122). 



§ 571. Cothurnocystis introduces an entirely novel plan of Echinoderm structure, 

 and, as such, receives detailed description (§§ 160-260). Here it will be enough to 

 mention the existence of fifteen or more separate openings into the gullet. Each of 

 these may be regarded as a mouth ; they are not comparable to the numerous arm- 

 passages in Camerate Crinoids, all of which lead to a single subtegminal mouth. 



§ 572. Trochocystis. The relations of the intake and vent are discussed and my 

 previous account corrected ; the supposed anal process proves to be the hypostome of 

 a Paradoxides (§§ 246-252). 



§ 573. Ceratocystis. Details are added to the previous description ; the resem- 

 blances to Cothurnocystis are thus made apparent, and a fresh interpretation of the 

 internal anatomy necessitated (§§ 255-258). 



Rhombifera. 



§ 574. Cheirocrinus. An analysis of the theca based on C. constyictus enables the 

 plates, especially in the upper circlets, to be homologised with greater accuracy and 

 confidence (§§ 293-296). The same species also affords valuable evidence as to the 

 structure of the tegmen and the relations of the subvective grooves (§§ 323-326). The 

 distribution of the pectinirhombs is discussed in the light of recent evidence, and the 

 absence of pectinirhomb 1-6 from C. constrictus is noted as peculiar (§§ 298-300). 

 The structure of the stem is discussed (§§ 304-306), and it is concluded that the roots 

 described by Jaekel do not belong to this genus. 



§ 575. Pleurocystis. The homologies of the thecal plates are expounded, certain 

 corrections are made in previous accounts (§§ 366-369), plate 13 is admitted to be 

 absent and its fate discussed (§§ 370-372), an attempt is made to elucidate the com- 

 position of the tegmen and the orientation of the brachioles (§§ 373, 374). The 

 number, relations, and shape of the pectinirhombs are considered, and the reduction 

 or suppression of pectinirhomb 1-5 in some of the British species is now first noted 

 {§§ 375-378). The enlargement of the periproct in the British species is described, 

 and estimates as to the number of periproctals are corrected (§§ 380, 381). The 

 downward extension of a rectal lobe, which is a conspicuous feature in some of 

 these species, leads to a brief discussion of Jaekel's views as to the coil of the gut, 

 and its relations to the parietal septum (§§ 382-384). The structure of the stem is 

 described from fresh evidence (§§ 385-389). 



in. Taxonomy. 

 The following is a brief summary : — 



§ 576. The Order Amphoridea is retained provisionally (§ 13). 

 The Class Carpoidea of Jaekel is rejected (§ 16), but its Order Heterostelea is 

 retained and rediagnosed as a Suborder of Amphoridea, with the Families : Dendro- 



