THE MOUNT DESERT REGIOX 347 



The zooecia are large, rather tubular in form, thick-walled, 

 with 3 or 4 digitate processes of the peristome, which may 

 or may not bear rounded avicularia. The zooecia are raised 

 anteriorly and the peristome is high, quite obscuring the pri- 

 mary aperture. The ooecia are small, globular, and imper- 

 forate. 



PoRELLA PLANA Hiucks, 1888. PL 13, fig. 1. (Whiteaves, 

 1901, p. 104 (P. sJienei, var. plana), Gulf of St. Lawrence.) 

 Apparently very rare. It is an Arctic and high northern 

 species, though Hincks described it from the Gulf of St. Law- 

 rence. Probably Mt. Desert Island is about the southern limit 

 of its range. 



The zoarium becomes erect and branched from an encrust- 

 ing base, the branches flattened and lobate. The zooecia are 

 large and regularly disposed, with a row of marginal pores, 

 few in number. At first glance the species seems to resemble 

 P. skenei rather closely, but the suboral umbonate processes, 

 1 to 3 in number, so characteristic of that species, are lacking 

 entirely, except in very young stages, when a small umbonate 

 process (avicularian chamber) is present above the middle of 

 the proximal border of the aperture. This soon becomes cov- 

 ered in and the avicularium obscured. There are two lateral 

 processes, one on each side of the aperture, bearing avicularia 

 with rounded mandibles turned more or less toward the aper- 

 ture. The ooecium is like that of P. shenei, but is somewhat 

 larger. 



Celleporidae Busk, 1852 

 ScHiZMOPORA MacGillivray, 1888 



SCHIZMOPORA CANALICULATA (Busk), 1884. PI. 13, figS. 4-5. 



(Osburn, 1912, p. 239 (Cellepora), synonymy and references; 

 Whiteaves, 1901, p. 109 {Cellepora), Gulf of St. Lawrence.) 

 Occasionally on hydroid stems, dredged at stations 15, 90, 94, 

 95, 96, 105, 107, and 149. This fine species is not recorded 

 elsewhere than on the New England and southern Canadian 

 coasts. Busk described the species from near Halifax, Nova 

 Scotia, since when it has been noted in the Gulf of St. Law- 

 rence, near Cape Sable, Nova Scotia, and about Cape Cod. 



