Haddon and Dixon — The Structure of PeacJua liadata. 401 



the two species in question, we do not propose to alter tlie specific 

 name which is in general use, as the name Actinia cylindrica was 

 pre-occupied by Eenier in 1804 (Prodromo di osservazioni sopra 

 alcuni animali, p. 23), and though not now retained in use, being 

 synonymous with Cerianthus membranaceous, Spallanzani, 1784, 

 this priority is sufficient to prevent the adoption of Eeid's specific 

 name. Furthermore, Eeid's description and figures are meagre 

 and unsatisfactory, whereas Gosse's account and drawings are 

 sufiiciently lucid to enable one to readily identify the animal. 



There is no doubt that Gosse has priority in the generic name, 

 therefore we cannot follow Andres in calling it Siphonactinia 

 hastata.^ 



Description. 



Form. — Column only divided into capitulum, scapus, and physa, 

 when fully distended. When contracted the column is rugose, but 

 smooth when fully distended ; it is furnished with numerous minute 

 suckers. The physa is very variable in size and completely retrac- 

 tile. Tentacles, twelve marginal, monocyclic, cylindrical, obtuse ; 

 when the animal is free they are usually carried more or less bent 

 forwards; when in its burrow, they lie at about right angles to 

 its length. Disc round, narrow, flat. Mouth large, but usually 

 masked by the conchula. Conchula (the free oval extremity of the 

 siphonoglyphe) varies greatly in complexity, having from six to 

 twenty lobes ; one basal and two lateral lobes may always be 

 detected, which are larger and carry more secondary lobes than 

 the remainder. The basal lobe forms a kind of lid or opercu- 

 lum to the siphonoglyphe. 



Colour. — Capitulum translucent, the oesophagus shining 

 through with a purplish colour. When the animal is in its 

 burrow the contracted capitulum has a corrugated greyish appear- 

 ance. When the tentacles are completely contracted, radiating white 

 linear spots are plainly seen on the capitulum ; the fundamental 

 number is twelve, but there is a tendency for them to become 



^ Peachia, Gosse, 1855, Trans. Linn. Soc, xxi. p. 267; Siphonactinia, Da.mels.sen 

 and Koren, 1856, Fauna litt. Norvegiae, ii., p. 87 ; cf. Ann. Mag. Kat. Hist. (2), 

 XX. 1857, p. 240. 



