368 DR F. A. BATHER. 



Suborder, Marginata. 

 Fam. Trochocystitidae. 



Genus : Trochocystites Barr. 

 Fam. Mitrocystidae. 



Genera: Mitrocystites Barr. emend. Jaekel, Mitrocystella Jaekel, 'I Ateleocystites 

 Billings. 



Suborder, Soluta. 



Fam. Rhipidocystidae, 



Genus : Rhipidocystis Jaekel. 

 Fam. Dendrocystidae. 



Genus : Dendrocystites Barr. 



§ 27. The need for so elaborate a classification is not apparent, and it does not seem 

 to me that our present knowledge is sufficient to support it. Many of these forms are 

 very little known, especially the new genera and species proposed by Dr Jaekel him- 

 self In several other cases the interpretation of structure is admittedly speculative, 

 and often, I believe, erroneous. 



§ 28. Ceratocystis, whether Dr Jaekel's interpretation be correct or not, is a very 

 distinct genus, and is no doubt rightly placed in a separate Family (§ 256), but I am 

 unable to agree that the three obscure species of Barrande should be placed with it, 

 or even, as Dr Jaekel suggests, in an allied Family by themselves. 



§ 29. The position of the Anomalocystidae in a distinct Suborder from the Mitro- 

 cystidae seems incompletely justified, even if one goes so far as to accept the division 

 into two Families. 



§ 30. It may be convenient to place Trochocystis in a separate Family (§§ 246-254). 



§ 31. Rhipidocystis is so little known, or at least so inadequately described, that one 

 does not grasp its relation to Dendrocystis, or the need for placing these two genera 

 with their three or four species in a Suborder by themselves (§ 35). 



§ 32. The new genus Cothurnocystis (§ 162) combines the main distinctive feature 

 of the Cornuta with that of the Marginata, and in other respects necessitates a re- 

 valuation of the whole evidence. Further discussion must be deferred till the new 

 facts provided by this and by the Girvan specimens of Dendrocystis have been set 

 forth. Meanwhile enough has been said to explain why I drop Dr Jaekel's classifica- 

 tion and merely arrange the genera of Heterostelea in Families as follows : — 



Dendrocystidae. 

 Rhipidocystidae ? 

 Ceratocystidae. 



Cothurnocystidae. 

 Trochocystidae. 

 An omalocy stidae. 



Fam. Dendrocystidae. 



§ 33. Diagnosis. — Amphoridea Heterostelea with a theca broader towards the 

 column and composed of numerous plates irregular in size, form, and arrangement. 



