THE MOUNT DESERT REGION 349 



Alcyonidiidae Hincks, 1880 

 Alcyonidium Lamoiiroux, 1821 



Alcyonidium polyoum (Hassall), 1841. PI. 5, figs. 5-7, 

 (Osbiirn, 1912, p. 251 {A. my tilt), synonymy and references.) 

 Frequent at both shore and dredging stations, encrusting 

 stones, shells, and at station 14 extraordinarily abundant on 

 Laminaria stems. Noted at six shore stations and twenty- 

 two dredging stations. Banging from Arctic seas, Spitz- 

 bergen, and Greenland, southward on both sides of the At- 

 lantic to France and southern New England, on the Pacific 

 coast to British Columbia, and Harmer reports it for the 

 Torres Straits. Strange to say, it has not been reported for 

 eastern Canada, though I have specimens from Hudson Strait. 



In the ''Report on the Bryozoa of the Woods Hole Region," 

 Osburn listed the species under the commonly accepted name, 

 A. mytili Dalyell, with the suggestion that it might be synony- 

 mous with Hassall 's Sarchochituin polyoum. Since then Har- 

 mer (1915, p. 37) has discussed this question and has accepted 

 the synonymy. 



The zoarium is encrusting, forming rather firm, dingy white, 

 yellowish, reddish, gray, or brown colonies, sometimes quite 

 dark, at other times almost transparent. In young, rapidly 

 growing colonies the layer may be very thin and transparent, 

 in older stages the gelatinous zooecial wall thickens. There 

 is a good deal of variation in appearance in the diiTerent 

 stages, to which the differences in color add more variety. 

 Verrill described the red variety as a new species, A. ruhrum. 

 The surface of the zooecium is smooth, except where the re- 

 tracted polypide forms a small papilla near the middle of the 

 frontal wall. 



Alcyonidium parasiticum (Fleming), 1828. PL 5, figs. 3-4. 

 (Osburn, 1912, p. 251, references.) Dredged at fourteen 

 stations, encrusting the stems of hydroids, etc., one colony 

 on the carapace of a Hyas. The species occurs on both sides 

 of the Atlantic, on the European side from Spitzbergen to the 

 British Islands, but on the American side it has not been 

 reported farther north than the present record, while it ex- 

 tends south to the Chesapeake Bay. 



