REPORT ON THE ALCYONARIA. ll 



scales or spiny needles. The spines or thorns usually project beyond the surface of the 

 cccnenchyma, and give it a rough or spiny appearance. In the polyps are distinguishable 

 a calycine (not retractile) region, a median oesophageal region, and a tentacular region. 

 The median region can be withdrawn into the calycine portion, so that in the retracted 

 state the tentacular portion rests directly upon the calycine margin. Around the bases 

 of the tentacles lies a ring of peripherally disposed calcareous spindles, forming the collaret. 

 The tentacles fold together down upon the calyx; their bases are well furnished with 

 spicules. When the polyp is contracted the armoured tentacle-bases form an eight- 

 rayed oj)erculum, closing up the calyx. 



This family is the richest in specific forms of the Holaxonia. These may be grouped 

 into several genera, chiefly diagnosed from the shape of the spicules, besides which 

 there is to be taken into account the more or less different methods by which the tentacles 

 are retracted within the calyx. This retraction is least developed in Acanthogorgia and 

 Muriceides, w^hich are, as regards their polyps, nearest perhaps to the Ceratoisidinse. 

 The power of retraction increases, however, in the succeeding genera, until in the case of 

 Muricea, complete concealment within the calyx becomes possible. This last genus 

 forms a transition to the Plexauridse. 



In the subjoined list, all the genera which have been fully diagnosed by Vcrrill in 

 his various memoirs are accepted. Of the numerous genera recorded by Gray, only those 

 are retained whieh have been reinvestigated either by Ridley or the authors. Gray's, 

 diagnoses being based upon very trivial characters are in most cases insufficient. 



1. Acanthogorgia, Gray, emend. 



Verrill. 



2. Paramuricea, KoUiker, emend. 



Verrill. 



3. Hyjmogorgia, Duchassaing and 



Michelotti. 



4. Muriceides, Wright and Studer. 



5. Anthomuricea, Wright and Studer. 



6. Clematissa, Wright and Studer. 



7. Villogorgia, Duchassaing and 



Michelotti, emend. Ridley. 



8. Anthogoi-gia, Verrill. 



9. Menella, Gray. 



10. Placogorgia, Wright and Studer. 



11. Echinomuricea, Verrill. 



12. Echinogorgia, KoUiker. 



13. Menacella, Gray, emend. Ridley. 



14. Heterogorgia, Verrill. 



15. Astrogorgia, Verrill. 



16. Behnjce, De Phillipi. 



17. Acamptogo7'gia, '^n^\t and Studer. 



18. Thesea, Duchassaing and Michelotti. 



19. Ads, Duchassaing and Michelotti. 



20. Elasmogorgia, Wright and Studer. 



21. Muncella, Verrill. 



22. Eumuricea, Verrill. 



23. Muricea, Auct, emend. VerriU. 



