226 J- Playfair McMüerich, 



Family Actiniidae G-osse. 1858. 



Actininae with an adherent base. Column wall smootli or pro- 

 vided with Verrucae, but never with hollow vesicular outgrowths. 

 Sphincter endodermal, diffuse or rarely aggregated, usually weak. 

 Tentacles simple, cyliiidrical ; margin smooth or provided with simple 

 acrorhagi. Mesenteries in several cycles of which usually more than 

 one is perfect; longitudinal muscles usually diffuse; parieto-basilar 

 and basilar muscles unequally developed. No acontia. 



The history of the term Actiniidae is somewhat complicated. It 

 was, so far as I am aware, first employed by Johnston (1838) and 

 later by GtOsse (1855) in a sense almost equivalent to Dana's Acti- 

 niaria, and it was not until 1858 that Gosse limited it so as to 

 include only the genera Anfhea and Actinia. It is employed here in 

 the sense in which it is understood by Haddon (1898), with the 

 important modiflcation that the genus Bolocera and its allies are ex- 

 cluded, and it is practically equivalent to the family Antheadae as 

 recognized by Carlgren and myself in 1893, although additional 

 genera have been added to it since that time. 



Genus Gyrostoma Kwietn. 1897, 



Actiniidae without acrorhagi, Verrucae or collar; tentacles mo- 

 derate or Short, sphincter weak, usually diffuse. 



Since Hertwig (1882) showed that Anemonia sulcata possessed 

 acrorhagi a strict distinction of that genus from Actinia has been a 

 matter of some difficulty. I suggested at one time (1893) that it 

 might be advisable to limit the genus Anemonia to forms destitute 

 of acrorhagi, even although this would bring the type species within 

 the genus Actinia, and Haddon (1898) states it as his opinion that 

 the genus "stands or falls according to whether the puffy capitular 

 rim of A. sulcata is to be regarded as destitute of, or possessing 

 acrorhagi". The genus Anemonia is, accordingly, in a somewhat 

 precarious condition, and yet it is one of the oldest genera of the 

 group, having been founded by Eisso in 1826. 



It seems to me that a distinction may be found between 

 Anemonia and Actinia in the nature of the tentacles, their length 

 and feeble contractility in the former genus being very characteristic. 

 But if this be taken as the principal distinction and both genera 

 be credited with acrorhagi, then it becomes necessary to place in 

 another genus those forms which have been referred to Anemonia 



