CLASSIFICATION OF ACTINIARIA 259 



Genera : Actinernus, Synactinernus, Isac- 

 tinernus, Synhalcurias. 



V 



Actinernus, Verr., 1879. 



This is only part of Verrill's genus. Other forms sometimes 



assigned by mistake to it will be found under Actino- 



s c y p h i a and Polysiphonia. 

 Porponia, Hertw., 1882, p. 125. 

 8ee Carlgren, 1914 ; Carlgren, 1918, p. 31, &c. ; Stephenson, 



1918 B, p. 127 ; Stephenson, 1920 a, p. 540. 

 Not Actinernus as used for A . p 1 e b e i u s , A . s a g i n a - 



t u s , A . a u r e I i a . 



Actinernidae with thick body which expands more or less distally, 

 and is often but not always lobed, the lobes usually eight in niunber. 

 Tentacles (except the youngest and sometimes the inner ones) wilh 

 aboi'al mesogloeal swellings or bridges of varying development in 

 different species, whicli may run up the tentacles almost to their tips. 

 The tentacles usually in two cycles, and largest at the apices of the lobes. 

 Numerous mesenteries, the older ones developed as usual in Endo- 

 coelactaria ; after a certain point, however, they continue to appear 

 in definite zones in a bilateral way, from the outer side of the zone 

 inwards, usually. These mesenteries have the partners of a pair unequal. 

 Mesenterial muscle weak. 



Species : 



A. nobilis, Verr., 1879, p. 474. (See Carlgren, 1918, p. 32.) 



A. elongatus, Hertw., 1882. p. 111. (See Carlgren, 1918, p. ^3.) 



A, robustus, Hertw., 1882, p. 11.3. (See Carlgren, 1918. p. 34.) 



A. michaelsarsi, Carlgr., 1918, p. 33. 



A. an tare tic us, Carlgr., 1914, p. .50; 1918, p. 35. 



Synactinernus, Carlgr., 1918, p. 30. 



Actinernidae with the body expanded above into eight lobes, four 

 larger and four smaller alternating. Tentacles in at least two cycles, 

 without basal swellings, largest at apices of the lobes, ninnerous. Radial 

 muscle of disc and tentacles chiefly ectodermal. At least half the 

 numerous mesenteries perfect. Mesenterial muscle not forming pro- 

 jecting retractors. The perfect mesenteries are cyclic in arrangement, 

 beyond these are others of unequal size in upper part of body. 



Species : 



S. Ilavus, Carlgr., 1918, p. 31. 



