264 
grøssern Annåherung der Hydranthen; das ergiebt den Thujaria- 
und den Dynamena-Typus, letzterer vielleicht zum Theil direct aus 
dem Sertularella-, zum Theil aus dem T7hujaria-Typus ableitbar. 
Noch gråssere Annåherung fihrt zur Entwicklung der Pasythea- 
Gruppe, zum Theil von Thujaria, zum Theil von Dynamena aus; 
ferner zur Selaginopsis- und zur Hydrallmania-Gruppe, beide von 
Thujaria aus." When Schneider lets the joints disappear in 
order to produce the Dynamena-type, he forgets that according to 
his own definition of this type it is characterized by the possession 
of a joint between each two pairs of hydrothecae. 
Of the six groups into which Schneider divides the Ser- 
tulariidae we have already regarded Selaginopsis, and we shall 
later speak about Pasythea and Hydrallmania on mentioning the 
systematic arrangement proposed by Professor Nutting. At this 
place, therefore, we have only to mention the groups Dynamena 
and Thujaria. 
Schneider characterizes the Dynamena-group in the following 
way: Die Hydrotheken opponirt, zwischen jedem Paar ein Gelenk; 
NES ER ; Mindung der Theca meist mit zwei vorgetåuschten (L e- 
vinsen) Zåhnen, Deckel einfach. — Hierher gehåren: Diphasia 
rosacea L., attenuata Hincks, fallax Johnston, pinaster Ell. 
et Sol., tamarisca L., pinnata Pallas., Sertularia pumila L., 
gracilis Hassall, operculata L.; Sertularia bispinosa Gray, 
minima Thompson, macrocarpa Bale." Of the species here 
named Diphasia rosacea, D. attenuata, D. fallax, D. pinaster and 
D. pinnata have no teeth and an adcauline opercular valve and 
belong to my genus Diphasia, while D. tamarisca must be referred 
to Sertularella as it possesses a tridentate hydrotheca. and three 
opercular valves.  Sertularia pumila, S. gracilis and S. minima 
belong to my genus Sertularia, as the bidentate hydrothecae 
possess an adcauline. collar and an abcauline opercular valve, while 
Sertularia opercularis, 8. bispinosa and S. macrocarpa must be 
referred to a new genus, Odontotheca. ne 
