CRRIANTHARIA. 41 



Type : Pachyccrianthus benedeni R o u 1 e. 

 Genus 2. Cerianthus delle Chiaje s. str. 



Cerianthidae whose and couple of protocnemes are long, fertile and provided with a small 

 region of the cnido-glaudular tract Arrangement of the metacnemes in each quartette Af, B, m, b 

 more or less distinct. M diminishing in length towards the multiplication chamber, occasionally with 

 some breaks in this diminution. 



Type: Ccriatithus mcmbranaceus Spall. 



Genus 3. Ccriantheopsis nov. gen. 



Cerianthidae, whose 2nd couple of protocnemes are long, fertile and provided with a very 

 small region of the cnido-glandular tract. Arrangement of metacnemes in each quartette m, B, M, b 

 more or less distinct. M increasing in length towards the multiplication chamber, with (or without?) 

 some breaks in this increase. 



Type: Ceriantheopsis americanus (Verrill). 

 Larval genera: Solasteractis E. van Beneden. 

 lApiactis E. van Beneden. 

 IPeponactis E. van Beneden. 

 Family 2 Acontiferidae^. 



Ceriantharia with acontium-like threads from the craspedion region, whose ectoderm chiefly 

 consists of mucus cells, on two or more mesenteries. 



Genus 4. Arachnanthus nov. gen. 



Acontiferidae whose 2nd couple of protocnemes are comparatively short and sterile. Metacnemes 

 of the ist and 2nd cycles (M, m) without region of the cnido-glandular tract but with "acontia" on 

 the best developed. Arrangement of metacnemes in each quartette M, B, m, b more or less distinct 



Type: Arachnanthus oligopodus (Cerfontaine). 

 Larval genera: Arachnactis 2 } M. Sars. 



Ovactis E. van Beneden. 

 Dactylactis E. van Beneden. 

 lApiactis E. van Beneden. 

 ? Peponactis E. van Beneden. 

 Family 3. Botrucnidifcridac. 

 Ceriantharia with cnidorages mostly aggregated in botrucnidae; without "acontia". 



') This name ought properly to be replaced by another, since, as I have shewn below, the "acontia'' of the Ceri- 

 antharia do not answer to the "acoutia" of the Actiniaria. 



2 ) Me. Murrich is probably right in his view that Arachnactis bourne: and A. brachiolata must be removed from the 

 genus Arachnactis. If the first is the larval form of Cerianthus lloydii, which is extremely likely, it naturally cannot retain its 

 place under the family Acontiferidae. Unfortunately the known larval stages of this species are all so early that "acoutia", 

 even if they do appear eventually, have not had time to form. For the oldest larval stage observed by me had only 5 couples 

 of mesenteries only 3 of which possessed filaments. The couple on which "acontia" ought to appear, if such really do form, 

 had only feebly developed filaments. The classification of A. bournci remains therefore for the present uncertain. The same 

 holds true also of A. brachiolata. 



The Danish Ingolf-Expedition V. 3. 6 



