Stephknson — Certain Actiniaria collected off Ireland 111 



tudinal musculature on that surface of the mesentery facing the adjacent 

 macromesentery, though it can hardly be spoken of as a retractor. PI. XX, 

 tig'. 9, shows the arrangement of mesenteries on one side of the animal (note 

 that there is 1 actinopharyngeal groove only), ami PI. XIX, fig. 1, shows the 

 muscular portion of a macromesentery and the whole of the adjacent micro- 

 mesentery at a fairly low level. 



There are, apart from the larger micromesenteries, representatives of two 

 cycles (apparently incomplete cycles) of smaller ones, confined entirely to the 

 underside of the oral disc, and developed of course in the endocoels formed by 

 the macromesenteries with the primary micromesenteries. 



There is one question which is naturally raised by this species— Ts it not 

 simply a young form of some species of Halcurias, and therefore not entitled 

 to generic distinction ? Of course this may be so; but I incline to think that 

 the form is really not very far from adult, and is entitled to generic distinction, 

 for the following reasons. 



The largest specimen investigated (and not much larger than the others) 

 possessed well-developed testes; and although a small animal, was not much 

 smaller than, for instance, Halcurias pilatus, if at all. Then, if the 4 pairs 

 of micromesenteries are to become macromesenteries — and a great deal of 

 development, above all the specialization of a great retractor muscle, is 

 necessary for the accomplishment of this (a condition which would be 

 required to convert the form into a Halcurias) — one would expect them to be 

 more advanced than they are by the time that the animal has reached its 

 present size and has acquired gonads and tertiary mesenteries. So I have 

 thought it best to erect a new genus for the species, which will stand unless 

 it should be proved in some way that the young Halcurias resembles 

 Carlgrenia. 



Family BOLOCERIDAE McMurrich. 



Actiniina with well-developed base and basilar muscles. Sphincter 

 endodermal, variously developed, or absent; if present, may be diffuse or 

 circumscribed. Usually numerous mesenteries perfect. Tentacles attached 

 to the oral disc by a very short thin-walled neck, and usually provided each 

 with a sphincter muscle above the neck, by means of which the neck may be 

 torn, in which case the tentacle is lost. 



Bolocera Gosse. 



Boloceridae with well-developed endodermal sphincter-muscle, which is 

 diffuse. Tentacles with well-developed sphincters. Numerous perfect 

 mesenteries (i.e., more than 6 pairs). 



