Stephicnson — Certain Actiniaria collected off Ireland. \~11 



quite exactly. Carlgren's specimen had 6 - 12 - IS - 36 ; and Gosse gives 

 6-6-12-36. 



In two dissected specimens, one had 16 pairs of perfect mesenteries, 

 the other had 1 extra perfect unpaired mesentery. Both had a cycle of 

 moderate-sized imperfect pairs alternating with the perfect ones, and a last 

 cycle, consisting mainly of small unpaired mesenteries, only well developed 

 near the base, and sometimes with a still smaller partner. After careful 

 investigation of the whole of these two animals, I cannot at all satisfy myself 

 that the rule which prevails in connexion with the smaller mesenteries of 

 Actiuostola is carried out with any definiteness. It does hold good for 

 some sectors of the animal, but is not, as far as I can tell, general. It 

 seems to me too imperfect, here, to warrant the inclusion of the genus in the 

 Actinostolinae. 



Actinernus Verrill. 



Paractinae, with pedal disc of variable extent — it may be broad, or so 

 reduced as to be practically absent ; or it may be concave, secreting a cuticle 

 and enclosing mud. Column with a smooth wall, which is sometimes so 

 thick that it forms a jelly-like coating to the body, so that the general form 

 may resemble that of a Scyphozoan. Tentacles arranged in two cycles only, 

 at the extreme margin of the oral disc; they all have aboral basal swellings 

 of mesogloea, which are continuous with the body-margin, at least in the 

 case of the outer ones. Longitudinal muscles of the tentacles and radial 

 muscles of the disc entirely ectodermal. Oral disc wide, sometimes lobed. 

 Only six pairs of perfect mesenteries, with weak, diffuse retractors. 



The species which have hitherto been described under the generic name 

 Actinernus are four in number. The type is A. nobilis, Verrill, and it is 

 unfortunate that its anatomy is unknown. Carlgren (8), from an external 

 examination of a specimen of it, is inclined to think that it may really be a 

 Porponia. A description will be found below of an anemone which I believe 

 to be identical with the second species described — A. sag Verrill, 1SS2. 



This is certainly not a Porponia, since it has the normal mesenterial arrange- 

 ment, only six pairs of mesenteries perfect, and a mesogloeal sphincter. The 

 anatomy of A.plcbcius, McMurrich, 1893, brings it into line with A. saginatus, 

 and I am now able to describe a new species {A. aivrelia), with the same 

 esseutial structural features. The anatomy of A. sp., Haddon, 18S8, is 

 unknown. 



If it should prove in the end that A. nobilis is a Porponia, some readjust- 

 ment of names may be necessary; but in any case. A. sagina kins, 

 and aurelia go together and form one good genus. McMurrich (1S93) 



