STYLASTERIDAK 15 



The female gonophore in its fundamental features is constructed as in Stylaster gemmascens. 

 But its spadix is simpler in structure (PI. V figs. 47 and 48); it is bowl-shaped. Whilst the spadix 

 in Stylaster gemmascens develops blind sacs in the direction towards the central parts of the gono- 

 phore, all the blind sacs in Stylaster roseus lie along the periphery of the gonophore. The structure 

 may here be said to be more primitive than in Stylaster gemmascens. 



The synonymy of the species is not easily determined with certainty from the literature. No 

 differences between the available colonies and the old descriptions of Stylaster rosetts can be found. 

 As the species is the commonest Stylasterid in the Atlantic north of the equator, it is probably the 

 same form that served as a basis for Pallas' description of Madrepora rosea; the name also agrees with 

 the colour as noted by the collectors of the present material. The only disagreement to be noticed 

 between these colonies and Milne-Edwards' description (1857 p. 130) is, that the small branches 

 seldom show coalescences; but this character is of little importance and can scarcely be considered 

 sufficient as a specific distinction. Pourtales (1871 p. 34) under the name of Stylaster erubescens 

 describes a species from the deeper layers at Florida; his excellent figures show at once, that it can- 

 not be specifically distinct from the North Atlantic Stylaster roseus; on the other hand, it is exceeding v 

 doubtful if it is this species which he (1. c. p. 83) with doubt refers to Pallas' species as Stylaster 

 roseus. P. M. Duncan {1874 PI. 49 figs. 13—15) figures the species from the Faeroe Channel, but refers 

 it erroneously to Stylaster gemmascens. Stylaster rose/is is common in the northern Atlantic south of 

 the submarine ridge between Scotland— Iceland and Greenland. 



Subgenus Allopora (Ehrenberg) 

 Stylaster norvegicus (Gunnerus) 

 1768 Millepora norvegica, Gunnerus, Om nogle norske Coraller p. 64, Tab. II figs. 20—22. 



1873 Allopora norveg/ca, G. O. Sars, Dyrelivet paa vore Havbanker p. 45. 



1874 Stylaster gemmascens pars, P. M. Duncan, Madreporaria . . . "Porcupine" p. 332, PI. 49 figs. 1—3. 

 1881 Allopora oculma, Moseley, Stylasteridae, "Challenger" p. 85. 



^82 norvegica, Storm, Bidrag til Kundskab om Trondhjemsfjordens Fauna, IV, p. 26. 



Z 888 — oculma + A. norvegica, Hickson, On the maturation of the ovum and Development of 

 Allopora p. 595. 

 The fan-shaped colonies are generally branched in one plane; they are not recurved and show 

 no distinct division into stem and branches. The cyclosystems are arranged irregularly; they are most 

 numerous on the front surface of the colony. They are circular or more rarely somewhat oval and 

 have from 5 to 9, in general 6—7 quite separate dactylopores, each with a faintly developed dactylo- 

 style. By means of a shallow incision the gasteropore stands in communication with the dactylopore. 

 The gasterostyle is approximately spherical, of the same height as breadth. The gasterozooid has 

 from 5 to 7, in most cases 6 quite small tentacles. — The ampullae are deeply imbedded and are hardly 

 seen on the surface of the colony. The male ampullae contain in general 3, seldom 2 or 4 gonophores. 

 The surface of the colony is smooth, not reticulated. 



