THE MOUNT DESERT EEGION 335 



and later becomes involved in the secondary crust. The zooe- 

 cial aperture of a specimen from Ph^mouth, England, meas- 

 ures 0.079 mm. in length by 0.102 mm. in width, on the aver- 

 age ; the zooecia average 0.47 mm. long by 0.85 mm. wide. 



Smittina reduplicata n.sp. PL 11, fig. 9; pi. 13, figs. 2-3; 

 pi. 14, figs. 9-10. (Osburn, 1912, p. 247; 1912 a, p. 283 {Po- 

 rella concinna, pars.) Encrusting stones and shells, common, 

 taken at three shore stations and twenty-five dredging sta- 

 tions. The species is also represented in the author's collec- 

 tion from Great Round Shoal, off Nantucket Island, from 

 Crab Ledge, off Cape Cod, from the Isles of Shoals, and from 

 Shoal Tickle, near Nain, Labrador. 



Zoarium in younger stages forming a semitranslucent, 

 rather regular and even crust; in older specimens, with the 

 increase in calcification, the presence of ooecia and secondary 

 avicularia, becoming rough and white. Colonies an inch or 

 more across have been observed. Zooecia somewhat elongate, 

 regularly disposed where the substratum permits, broadest a 

 little back of the aperture, the frontal surface regularly 

 rounded from side to side and rising gradually from the base 

 toward the aperture. The pores are limited to a marginal 

 row, usually about twenty in number, which are separated by 

 strong ribs which run only a short distance toward the center. 

 In secondary calcification the frontal wall becomes very thick 

 and the ribs continue to rise between the marginal pores, 

 which are strikingly evident even in advanced stages. The 

 primary aperture is semicircular, a little narrowed posteri- 

 orly, without cardelles, and with a very broad lyrula (resem- 

 bling that of concinna, but much broader). The operculum 

 has oblique sclerites and there are two small oral spines. A 

 small rounded avicularium is situated on the proximal border 

 of the aperture, as in concinna, but its chamber is more ven- 

 tricose and broader, continued outward on the sides to the 

 margin. In the infertile zooecia there remains this single 

 avicularium, but in the fertile individuals a secondary avicu- 

 larium of the same shape and size surmounts the first as 

 the peristome rises. Occasionally this secondary avicularium 



