ACTINIARIA 



than the outer, the latter without stinging battery at the base. longitudinal muscles of the tentacles 

 and radial muscles of the oral disc mesogloeal. 2 deep siphonoglyphes. Mesenteries hexamerously arranged, 

 but not always regularly, at least the first 2 cycles perfect. longitudinal muscles of the mesenteries form 

 no distinct pennons. Parietobasilar muscles more or less strong. Reproductive organs on the mesenteries 

 of the third and fourth cycles, sometimes also on some of the fifth. No differentiation into filament-lacking 

 fertile and filamentous sterile mesenteries. The weaker mesenteries, only in the most proximal part of the 

 body, without filaments and reproductive organs. 



The diagnosis which I have given here of the genus differs considerably from the original diagnosis, 

 proposed by Me. Murrich (1893). That this latter was not suitable, may be concluded from the fact that 

 Me. Murrich later on (1904 p. 245) has placed to the genus a species Pycnanthus (Paractis) lineolatus, which, 

 to my mind, cannot be conjoined with the type, maliformis. In P. lineolatus the longitudinal muscles of the 

 tentacles and the radial muscles of the oral disc namely are ectodermal, its perfect pairs of mesenteries are 

 only 6, and its reproductive organs are developed on the mesenteries of the second and third orders, characters 

 which differ so much from the type that they make it impossible to place both species to the same genus. 

 The reason why Me. Murrich has enclosed them in the same genus, is that both specimens are provided 

 with capitular ridges; I for my part am very sceptical as to the systematic importance of the capitular 

 ridges, at least of such as are here appearing, which may very well have arisen by the contraction of the 

 distal part of the column. Stephenson (1918 b p. 124) has drawn the same conclusion concerning Cym- 

 bactis (= Sicyonis compare p. 211) gossei. According to Me. Murrich, the ridges besides should not be of 

 the same structure in both species, in the type maliformis "hollow with rather delicate walls", in the species 

 lineolatus "solid." In the below described species P. laevis, which in all other important characters agrees 

 with the type, there are no distinct capitular ridges. I therefore think that the capitular ridges are without 

 importance as a genus character, having probably in many cases arisen by contraction. As I have introduced 

 them above in the diagnosis of the genus they might be used ; I will, however, declare that they seem to be 

 of small systematic importance. To the genus characters Me. Murrich also adds, that the tentacles are 

 "not swollen at the base". The below described P. laevis is, however, provided with such swollen tentacles. 



Me. Murrich 's Pycnanthus lineolatus must, to my mind, form a new genus type, with which possibly 

 also Paractis tenuicollis may be placed. For this genus Verrill (1899 p. 212) has proposed the name Atifi- 

 paractis, type : A . lineolatus, wliich may be characterized as follows. The diagnosis is based on Me. Murrich's 

 description of the type. 



Paractiidae with well developed basal disc. Column smooth, without tubercles, in contracted state 

 low and thin, sometimes with more or less distinct longitudinal ridges in the upper part. Margin tentaculate, 

 not lobed. Sphincter strong. Tentacles short, only half so numerous as the mesenteries (always?). Outer 

 tentacles without stinging batteries at the base. Longitudinal muscles of the tentacles and radial muscles 

 of the oral disc ectodermal. Actinopharynx long with two siphonoglyphes. Mesenteries hexamerously arranged, 

 only the 6 first pairs perfect. longitudinal muscles of the mesenteries forming weak, broad pennons. Repro- 

 ductive organs on the mesenteries of the second and third orders. No differentiation into filament-lacking 



fertile and filamentous sterile mesenteries. 



26 



The Ingolf-F.xpedition. V. 9. 



