THE MOUNT DESERT REGION 329 



The front of the zooecium is perforated by very large irreg- 

 ular pores, wliich sometimes give it the appearance of being 

 incompletely calcified, yet this appearance may be preserved 

 under secondary calcification. The rather large aperture is 

 rounded anteriorly, more straight on the proximal border, and 

 the presence of a pair of denticles gives the appearance of a 

 very broad sinus reaching almost the width of the aperture. 

 The peristome is often raised at the side of the aperture. The 

 semi-globose ooecium is also provided with a few very large 

 and irregular pores. A suboral avicularium is occasionally 

 present, separated somewhat from the aperture, but this is 

 wanting in Mt. Desert specimens. 



HippoDiPLOsiA PERTUSA (Espcr), 179-4—1797. PL 14, fig. 8. 

 (Osburn, 1912, p. 241 (Lepralia), synonymy and references; 

 Whiteaves, 1901, p. 101 (Lepralia), records and discussion.) 

 Apparently rare; only three small colonies were observed, 

 encrusting pebbles, dredging station 27. Cosmopolitan. On 

 the Atlantic coast of North America it is known from Green- 

 land to Florida. Hastings records it from the Galapagos 

 Islands (1930, p. 724). 



The front of the ooecium is thickly perforated, rather 

 smooth in young colonies, but granular in old specimens. The 

 aperture is almost round, but a pair of weakly developed den- 

 ticles give the appearance of a very broad shallow sinus at 

 the proximal border. The round ooecium is quite prominent, 

 and in secondary calcification the surface becomes rather 

 coarsely granular, with occasionally an umbonate process at 

 the top. A suboral umbo is present also in some zooecia. 

 There is no evidence of avicularia on Mt. Desert Island 

 specimens. 



HiPPODIPLOSIA RETICULATO-PUNCTATA (Hiucks), 1877. PI. 



10, fig. 2; pi. 13, fig. 6. (Whiteaves, 1901, p. 107 {Smittia), 

 Gulf of St. Lawrence; Osburn, 1912 a, p. 286 (Smittia), south 

 of Cape Sable, 45 fathoms.) Rare, one small colony with 

 ooecia, dredged at station 6, and one wdthout ooecia at station 

 27. The species has not been recorded this far south, but I 

 have a specimen from Cape Ann, on the coast of ]\Iassachu- 



