298 T. A. STEPHENSON 



In A ti t h e p s i s ( = S t i c h o d a c t i s) the condition is some- 

 times purely ' Actiniine ' — ^not more than one tentacle to each 

 exo- and endocoel ; but the more noimal state is for there 

 to be more than one tentacle ; or a row, on the older endocoels 

 but not tlie younger. 



In R a d i a II t h u s ( = H e 1 i a n t h o p s i s) comes the stage 

 where all the endocoels have radial rows, but there is only 

 about one row on each. In Stoichactis ( = Disco- 

 somoides) the last stage is attained, and there are not only 

 radial groups on all the endocoels, hut usually more than one 

 row abreast in each group ; and the tentacles have often 

 specialized in small size. As far as sphincters are concerned, 

 I think comparison with other families vn\\ show that their 

 exact form cannot be used here as a generic distinction. In 

 the lists of species given below it should be remembered that 

 a form here and there may be allocated to the ^^Tong genus 

 because of insufficient data about it ; but some re-arrangement 

 has been made intentionally to get the three grades clearlj* 

 separated off. The readjustments mainly mean a transference 

 to Antheopsis of some forms originally described under 

 Radianthus, Stichodactis, and Helianthopsis, 

 and a consequent depletion of the true genus Radianthus. 

 This has been necessary to get together all the forms with 

 radial rows of tentacles on the older endocoels only. It is not 

 much of a distinction, but if the two genera are to l.>e kept 

 apart at all it must be insisted on. That the sporadic occurrence 

 of a few cleft tentacles in some species should be used as 

 a generic character M'ould be a mistake. 



Stoichactis, Haddon, 1898, p. 472. 



D i s c s o m o i d e s , Haddon. 1 898, p. 470. 



Stoichactidae. Some species attain enormous size, up to about two 

 feet across, and often Crustacea or fish are commensal with them. The 

 body is usually wider above than below, and above with suckers which 

 may be in vertical rows — these may. however, be rudimentary or absent, 

 present or not even in the same species. Margin barely or slightly or dis- 

 tinctly marked, may be notched. Disc simple or little or much folded. 

 Tentacles not very long at best, usually short or very short ; digit if orm 



