8 



STYLASTERIDAE 



stylaster species may sometimes become so blown up and deformed that they may easily enough be 

 confused with the Allopora species. To facilitate the determination in difficult cases I give in the 

 following table their distinctive features. 



gemmascens 



norvegica 



Cyclosystems 



Gasterostyles 



Ampullae (9) 



with 12— 20, normally 14— iSdactylo- 



pores. Wall of gasteropore deeply 



incised towards the dactylopores. 



conical, twice as high as broad. 



near the surface and projecting like a 

 hemisphere; equipped with blunt spines 



with 8 -16, normally 9 — 11 dactylo- 

 pores. Wall of gasteropore slightly 

 incised towards the dactylopores. 



almost globular with same breadth 

 as height. 



near the surface and projecting like a 

 hemisphere; without spines. 



with 5—9, normally 6—7 dactylo- 

 pores. Wall of gasteropore slightly 

 incised towards the dactylopores. 



almost globular with same 

 breadth as height. 



deeply embedded, scarcely seen 

 externally on the colony. 



1873 



?i8 74 

 1879 

 1881 

 1882 



Subgenus Eustylaster nov. 



Stylaster gemmascens (Esper) Milne-Edwards et Haime. 

 1768 Madrcpora virginea, Gunnerus, Om nogle norske Coraller p. 56, Tab. VIII, figs. 2—4. 

 nee 1758 Madrcpora virginea, Ljnne, Systema naturae ed. X, vol. I, p. 798. 

 ? 1797 Madrcpora gemmascens, Esper, Fortsetzungen der Pflanzenthiere, T. I, p. 60, Tab. 55. 

 1857 Stylaster gemmascens, Milne-Edwards, Histoire naturelle des Coralliaires p. 130 '). 

 — , G. O. Sars, Dyrelivet paa vore Havbanker p. 45. 



, pars, P. M. Duncan, Madreporaria .... "Porcupine" p. 332. 



, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna p. 24. 



, Moseley, Stylasteridae "Challenger" p. 86. 



, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna IV, p. 25. 

 1910 , J. A. Thomson, Note on a Hydrocoralline from Rockall p. 61. 



1912 , Nordgaard, Faunistiske og biologiske iagttagelser p. 7. 



1912 — , Arndt, Zoologische Ergebnisse, I, p. 122. 



The fan-shaped colonies have as a rule a concave front surface and show a distinct difference 

 between stem, main branches and small branches. The cyclosystems are placed laterally and alternately 

 on the outermost small branches and their main axis forms almost without exception a pointed angle 

 of less than 45° with the axis of the branch; they are oval, except those just at the tip of the branch 

 which may be circular, and show from 12 to 20, normally however 14—18 quite separate dactylopores, 

 each provided with a rudimentary dactylostyle. The wall of the gasteropore shows deep incisions to- 

 wards the dactylopores. The gasterostyle is conical, twice as high as broad. The gasterozooid 

 has 4 quite small tentacles. - The female ampullae project like hemispheres above the surface of 

 the colony and when fully developed are equipped with 1 —7, generally 2 — 4 small, blunt spines. The 

 surface of the colony is smooth and indistinctly reticulated. 



Colour: white or faintly rose-red with darker yellowish red gasterozooids. 



Occurrence: west coast of Norway, Denmark Strait in 50—560111. depth, Rockall. (Indian Ocean?) 



'J This work contains a detailed list of the older synonymy. 



