Ven-i'll, Notes on Radiata. 461 



are notoriously variable in this group, and especially so in some north- 

 ern genera, like Urticina and Bxinodes. 



Suborder, A.CTINACEA VerriU. 



Actinina (fiiiuOy) ]"]Iirenberg, Corall. des rotlien Meeres, 1834. 



Actinidce (family) Dana, Zoophytes, p. 122, 1846. 



Actiniaires (pars) (suborder) Edw. and Haime, Corall., i, p. 224, 1857. 



Astrceacea (pars) (tribe) Gosse, Actinologia Britannica, p. 1, 1860. 



Actiniuce (subfamily) Duch. and Midi., Corall. des Antilles, 37, 1860, from Mem. 

 Reale Accademia delle Scienze, Turin ; ditto, {pars) (famUy) Supplement aux Co- 

 rall., 1864, from Mem. Reale Accad., xxiii, 1866. 



Actinaria (pars) (suborder) Verrill, Mem. Boston Soc, Nat. Hist., i, p. 14, 1863. 



Actinacea (Kwhorder) Verrill, Proc. Essex Inst., iv, p. 148, 1865; ditto, vol. v, p. 

 317, 1868. 



Polyps free and simple, rarelj^ compound, with a well developed 

 and muscular base, which is used both as an organ of locomotion and 

 adhesion. Tentacles varying in number from 1 to several hundred, 

 and quite varied in size and structure ; sometimes branched. 



The ambulacral spaces usually bear some other organs, such as 

 branchiae tubercles, suckers, colored spherules, and special pores. 



Family, Thalassianthid^ Verrill. 



Proceedings Essex Inst., iv, p. 148, 1865. 



Body more or less cylindrical in expansion, usually broad. The 

 disk bears various ambulacral organs in the form of simple or com- 

 pound tubercles, or arborescent and variously lobed branchiform or- 

 gans, in addition to, or replacing, the simple tentacles. Several of 

 these disk-appendages usually arise from each ambulacral chamber, 

 and when true tentacles are present, they may be outside or inside of 

 them, or on both sides. Base a flat locomotive disk. 



This family is almost confined to the tropical seas. It includes four 

 well marked subfamilies. 



1. Phyllactince Edw. and Haime. Disk bears both simple tentacles 

 and lobed tubercles, or compound branchiform appendages. 



2. Thalassianthincer (pars) Edw. and Haime. Disk bears large, 

 compound tentacles or branchiform organs, all of one form, without 

 simple tentacles. 



3. HeterodactyllncB Verrill. Disk bears large, compound, branchi- 

 form organs of two kinds. No simple tentacles. Includes Heterodac- 

 tyla Ehr. and Sarcophianthus Less. 



4. Discostominm Verrill {^lon Discosomoe D. and M.). The disk 

 bears small, tentacle-like papilla;, or small, sparingly lobed tubercles, 



