314 BIOLOGICAL SUKVEY OF 



quadrangular space. When the ooeciiim is present there are 

 usually two avicularia, one on either side, pointed forward on 

 the base of the zooecium in front of the ovicell. In the 

 absence of ooecia, a single avicularium is present, pointed 

 more or less backward. 



Amphiblestrum trifolium (S. Wood), 1850. PI. 14, fig. 2. 

 (Whiteaves, 1901, p. 97 (Memhranipora), for synonymy and 

 references; Osburn, 1912a, p. 279 (Memhranipora), for 

 further references.) Rare; found only a few times in the 

 collections on stones and shells. It ranges northward on both 

 sides of the Atlantic to the polar seas. 



As in the preceding species, the crj^tocyst extends over a 

 considerable portion, leaving a trifoliate membranous area. 

 Spines are usually wanting, and the tall spines of the pre- 

 ceding species are never present. Avicularia also are not 

 common and when present are placed on small elevations at 

 the border of the zooecium. The rounded ooecium bears a 

 more or less triangular area. 



Division V, Cellularina Smitt, 1867^ 



Scrupocellariidae Levinsen, 1909 

 ScRUPOCELLARiA Van Beneden, 1845 



Scrupocellaria scabra (Van Beneden), 1849. PI. 7, fig. 4. 

 (Osburn, 1912, p. 223, for references; Whiteaves, 1901, p. 93, 

 Grulf of St. Lawrence.) Common, attached to shells, stones, 

 algae, and the stems of hydroids and bryozoans, on hard 

 bottoms ; dredged at nineteen stations. Some specimens show 

 a tendency toward the northern variety, paenulata Norman, 

 in the size of the frontal scute. This is a well-known species 

 on the American coast from Cape Cod to Greenland; on the 

 eastern side of the Atlantic it occurs from Madeira to Spitz- 

 bergen. 



Whiteaves (1901, p. 92) lists 8. scruposa Linnaeus for the 

 Gulf of St. Lawrence, and Cornish (1907, p. 76, as S. elliptica 



^ Division III, Coilostega Levinsen, 1909, and Division IV, Pseudostega Levin- 

 sen, 1909, are not represented in the present collection. 



