626 Haddon and Shackleton — A Revision of the British Actinice. 



CLASSIFICATION OF THE GROUP. 



ZOANTHEiE. 



Actiniae with numerous perfect and imperfect mesenteries, and two pairs of 

 directive mesenteries, of which the sulcar are perfect and the sulcular are imperfect. 

 A pair of mesenteries occur on each side of the sulcular directives, of which the 

 sulcular moiety is perfect and its sulcar complement is imperfect ; a similar second 

 pair occurs in one section of the group (Brachycneminse), or the second pair may 

 be composed of two perfect mesenteries (Macrocneminse). In the remaining pairs 

 of mesenteries, of both divisions, this order is reversed, so that the perfect 

 mesentery is sulcar and the imperfect is sulcular. The latter series of mesenteries 

 are bilateral as regards the polyp and arise independently (i. e. neither in pairs nor 

 symmetrically on each side) in the exocoele on each side of the sulcar directives, 

 in such a manner that the sulcular are the oldest and the sulcar the youngest. 

 Only the perfect mesenteries are fertile or bear mesenterial filaments. A single 

 sulcar oesophageal groove is present. The mesogloea of the body-wall is traversed 

 by irregularly branching ectodermal canals or by scattered groups of cells. The 

 body-wall is usually incrusted with foreign particles. The polyps are generally 

 grouped in colonies connected by a coenenchyme, the coelenteron of each polyp 

 communicating with that of the other members of the colony by means of basal 

 endodermal canals. 



Family. ZOANTHID^, Dana, 1846. 



(With the definition of the group.) 



Sub-family. Beachycnemin^, n. s.-f.* 



Zoanthese in which the sulcar element of the primitive sulco-lateral pair of 

 mesenteries (cnemes) is imperfect : — 



GENERA AND TYPE SPECIES. 



ZoANTHUS, Lamarck. Type Z. sociatus (Ellis). 



IsAURUS, Gray. ,, /. tuberculatus, Gray. 



( ? Mammillifeea, Lesueur. ,, ilf. aMnc?«/«, Lesueur.) 



Gemmaria, Duchassaing et Michel otti. ,, G. rusei, Duch. and Mich. 



Palythoa, Lamouroux. ,, P. mammillosa(El\is and Sol.). 



Sphenopus, Steenstrup. ,, S. marsupialis, Steenstr. 



* Ppaxoi, short ; fiaKpo's, long ; kv»;/<.i;, a radius or spoke of a wheel. We have tried hard to discover a 

 short term for a mesentery, which would readily lend itself to combination with other words, but without 



