12 STYLASTERIDAE 



quite intact. It is probable indeed, that a fairly small opening is simply formed in the roof of the 

 ampulla, through which the larva escapes. This opening is at once closed again and the ampulla 

 persists for some time as a large empty space after the larva has escaped. The further fate of the 

 ampulla has not been observed. 



The synonymy of the species offers several difficulties. It is exceedingly doubtful, if it reallv 

 was this species which Ksper (1797 p. 60) described under the name of Madrepora gemmasccns and 

 the question cannot be settled from the literature. The reason for nevertheless retaining the specific 

 name gemmascens here is, that our commonest northern Stylaster, wherever it is mentioned in the 

 literature, appears under this name. Esper's specimens came from the Indian Ocean but no one 

 has later found the species there. - The first quite certain and detailed description of the species is 

 to be found in a treatise of Gunnerus (1768 p. 56), who erroneously identified it with Linne's Madre- 

 pora virginea; his drawings are the best which have ever been given of the species and the identification 

 is all the more certain because his specimens are still preserved in the Zoological Museum of Trondhjem. 

 One of them is reproduced in fig. 4 of PI. I. Gunnerus examined several colonies of this species from 

 the west coast of Norway, but his work has been passed over by later investigators and thus Esper 

 has erroneously been taken as the first describer. We thus find, that Milne-Edwards (1857) was still 

 unacquainted with the fact, that Stylaster gemmasccns lives in northern waters. It was reserved for 

 G. O. Sars (1872 p. 45) to point out its existence on the Norwegian coasts and he was the first to 

 refer the northern colonies to Esper's species. In this he is followed by P. M. Duncan, who how- 

 ever in his work on the material of the "Porcupine" (1874 p. 332) confounds it with Stylaster roseus and 

 Stylaster (Allopora) norvegicus; on the whole, to judge from his drawings it is extremely doubtful if 

 Duncan has had any specimens at all of Stylaster gemmasccns. Storm (1879 anc ^ 1881) found the 

 species again in the Trondhjem Fjord and points out that it is fairly frequent in its occurrence there. 

 Lastly, we find Stylaster gemmasccns mentioned from Rockall; through the kindness of Prof. J. A. 

 Thomson I have had the opportunity of examining his specimens, which are typical individuals of 

 the northern species; it is the only certain instance of its occurrence south of the submarine ridge between 

 Scotland —Iceland and Greenland. Excluding Esper's locality the species has not been found outside 

 the North Atlantic and even there it lives within a fairly restricted area. 



Stylaster roseus (Pallas) Gray 



1766 Madrepora rosea, Pallas, Elenchus Zoophytorum p. 312. 



1857 Sty/aster roseus, Milne-Edwards, Histoire Naturelle des Coralliaires T II, p. 130 '. 



1871 erubescens, Pourtales, Deep-Sea Corals p. 34, PI. IV figs. 10 and n. 



?i87i — roseus, Pourtales, I.e. p. 83. 



1874 gemmascens pars, P. M. Duncan, Madreporaria . . . "Porcupine" p. 332, PL 49, figs. 13 — 15. 



1877 roseus, Lindstrom, Contributions to the Actinology of the Atlantic Ocean p. 15. 



1878 erubescens, Pourtales, Corals . . . "Blake" p. 210. 



1881 roseus -\- S. erubescens, Moseley, Stylasteridae, "Challenger" pp. 86 and 87. 



l ) This work contains a detailed list of the older synonymy. 



