178 



PROF. ST. GEORGE MIVART ON 



Subsection 2. Diploconida. 



Skeleton a double one, with radii also. Grenus Dlploconus. 



Subsection 3. Cataphracta. 



Acanthometrida with outgrowths at right angles from their 

 radii forming a circumferential structure. Genera : Dorataspis, 

 Haliommatidium . 



Section y. POLTCYSTINA. 



Simple, ectolithic Eadiolarians with more or less compact ske- 

 letons, often with unipolar growth. No nuclear vesicle. 



Subsection 1. Cyrtida. 



Shell an external, more or less continuous, but perforated case 

 variously formed, mostly with an open mouth at one pole ; shell 

 growing from one pole. No radial skeleton except external spines. 



Subdivision i. Monocyrtida. 



Shell single, without divisions. Genera : Litharachnium, Cornu- 

 tella, Cyrtocalpis, Pylosp}i<jera, Spirillina, HalipTiormis, Halica- 

 lyptra, Carpocanium. 



Subdivision ii. Zygocyrtida. 



Shell divided by a vertical constriction. Genera : Dictyospyris^ 

 Ceratospyris, Cladospyris, Fetalospyris. 



Subdivision iii. Dicyrtida. 



Shell divided by a transverse constriction. Genera : Dictyocepha- 

 lus, Lophophcena, Clathrocanium, Lamprodiscus, Lithopera, Litho- 

 melissa^ Araclinocorys, DictyopJiimus, EucecrypJialus, Anthocyrtis , 

 Lychnocanium. 



Subdivision iv. Sticliocyrtida. 



Shell divided by two or more transverse constrictions. Genera : 

 Eucyrtidium, Lithocampe, Thyrsocyrtis, LitliocorytMum, Fteroca- 

 nium, Dictyoceras, Lithornithium, Ehopalocanium, Fterocodon, Po- 

 docyrtis, Dicty op odium. 



Subdivision v. Folycyrtida. 



Shell divided by several transverse or vertical constrictions. 

 Genera : Spyvidohotrys, Botryocampe, LitholotrySy Botryocyrtis. 



