498 T, A. STEPHENSON 
Sub-order ACTINIARIA. 
Tribe 1. Protantheae. 
Sub-tribe 1. Protactininae. 
Sub-tribe 2. Protostichodactylinae. 
Tribe 2. Nynantheae. 
Sub-tribe 8. Actininae. 
A. Athenaria. 
B. Thenaria. 
Sub-tribe 4. Stichodactylinae. 
Other arrangements ignore the Protantheae and Nynantheae, 
dividing at once into Actininae and Stichodactylinae, in 
which case the Protactininae rank as Actininae, the Proto- 
stichodactylinae as Stichodactylinae. 
The Protantheae are separated from the Nynantheae by 
the possession, usually, of an ectodermal muscle-sheet and 
nerve-layer in the body-wall and generally in the actinopharynx 
also; and in some of them by the absence of basilar muscles, 
and ciliated tracts on the mesenterial filaments. The Actininae 
and Stichodactylinae, and similarly the Protactininae and 
Protostichodactylinae, are marked off from each other by 
the fact that in the Actininae (and Protactininae) only one 
tentacle communicates with each exocoel and endocoel, at 
most, whereas in the other groups two or more tentacles grow 
out from at least the stronger endocoels. 
This section may suitably contain a list of the more generally- 
used families, which will be convenient for reference later, 
assigned to their respective positions under Carlgren’s main 
groups. 
1, PROTACTININAE: Gonactiniidae, Ptychodactidae, 
Halcuridae. 
9. PROTOSTICHODA CLYLINAR: Corallimor- 
phidae. 
3 ACTININAE; 
ArHENARIA: TIlyanthidae, Halcampidae, Halcampo- 
morphidae, Andvackiidae, Halcampactidae. 
