XIV ZOANTHARIA — CERIANTHIDEA 411 



about 15 mm. in length it has developed characters which are 

 sufficient to determine its position as a Cerianthid. 



The genus Cerianthus appears to be widely distributed. 

 C. vievihranaceus is the common species in the Mediterranean Sea, 

 but a smaller species has been described from Naples under the 

 name C. oligopodus by Cerfontaine. C. americanus occurs on 

 the eastern coasts of North America. The British and North 

 European species is C. lloydii, but another species, C. vogti, has 

 been found at a depth of 498 fathoms in the North Sea. C. 

 nohilis is a gigantic species supposed to be about 1 foot in length 

 when complete, from Torres Straits. 



C lathymetricus of Moseley, placed by Andres in the genus 

 Bafhyanthus, is a species of small size (25 mm.), obtained by the 

 "Challenger" from a depth of 2750 fathoms in the North 

 Atlantic. It exhibits a remarkable prolongation of the stomo- 

 daeum into the coelenteron in the form of a sack which con- 

 tained food. Moseley described a species of Cerianthus, 6 inches 

 long, living on the coral reef at Zebu in the Philippines fully 

 expanded in the tropical sunshine. 



Several species of Arachnactis larvae have been described. 

 Of these Arachnactis lloydii appears to be undoubtedly the 

 larva of C. lloydii. The adult forms of Arachnactis alUda from 

 various stations in the Atlantic Ocean and of Arachnactis 

 americana are not known. The larva of Cerianthus membranaceus 

 has been called Dianthea noUUs, and is characterised by the great 

 length of the column, by the general opacity of all parts of the body, 

 and by the precocious appearance of the median marginal tentacle. 

 A considerable number of remarkable pelagic larvae have been 

 described by van Beneden^ from the Atlantic Ocean, and pro- 

 visionally assigned by him to five different genera. The adult 

 forms of these larvae are not known, but they are probably 

 members of this order. 



1 E. van Beneden, Les Anthozoaires de la Plankton Expedition, Kiel, 1898. 



