NO. 3 OSBURN : EASTERN PACIFIC BRYOZOA CYCLOSTOMATA 727 



Family Alcyonidiidae Johnston, 1849 



Zoaria incrusting or erect in sacculate or cylindrical expansions. Aper- 

 ture closed by simple folds formed by the invagination of the tentacle 

 sheath when retracted, producing a puckered or drawn appearance. 



Genus ALGYONIDIUM Lamouroux, 1812 



Zoaria incrusting, coriaceous or gelatinous in appearance, forming a 

 soft cover over the substrata, or arising into lobed sac-like, or cylindrical 

 expansions. Zooecia closely united, not stolonate. The aperture may be 

 in the center of raised papillae, or the entire ventral surface of the 

 zooecia may present a smooth surface, a slight puckering at the distal 

 end indicative of the aperture. Genotype: Alcyonium gelatinosum Lin- 

 naeus, 1767. 



Key to the Species of Alcyonidium 



1. Zoaria primarily incrusting, spreading irregidarly 2 



Zoaria primarily erect, or disc-shaped, limited 4 



2. Zoaria flat, incrusting, zooecia irregularly hexagonal . . polyoum 

 'Zoaria. flat, incrusting, zooecia with raised apertures .... 3 



3. Zoaria argillaceous, zooecia with fine papillate border . parasiticum 

 Zoaria clear, zooecial aperture mammillate . . . mammillatum 



4. Zoaria disc-shaped, flattened disciforme 



Zoaria primarily erect 5 



5. Zoaria sacculate, expanded, lobed pedunculatum 



Zoaria elongate, cylindrical enteromorpha 



Alcyonidium polyoum (Hassall), 1841 

 Plate 77, fig. 1 



SarcochituTTi polyoum Hassall, 1841:484. 

 Alcyonidium mytili, Robertson, 1900:329. 

 Alcyonidium polyoum, Robertson, 1900:330. 

 Alcyonidium mytili. O'Donoghue, 1923:191; 1926:54. 

 Alcyonidium columbianum O'Donoghue, 1926:56. 



The zoaria of the specimens in the collection show a great deal of 

 color variation, ranging from transparent to brown or gray. In size the 

 colonies ranged from 1 to 6 cm in breadth depending upon the size and 

 type of subtrate. These zoaria are found incrusting rocks, mollusk 

 shells, algal holdfasts and sometimes on the larger Crustacea. 



