336 BIOLOGICAL SURVEY OF 



is not in the midline and more rarely there are two, more or 

 less symmetrically placed behind the aperture. Another type 

 of avicularinm, very small and with a pointed mandible, 

 occurs occasionally on the distal border of the aperture, con- 

 forming to the curve of the aperture, and, with secondary 

 calcification, opening into the orifice. This is difficult to see, 

 except in calcined specimens, and I have not observed it when 

 an ooecium is developed. The ooecium is hemispherical, prom- 

 inent, and in secondary calcification becomes thick-walled, but 

 is not at all immersed. It is imperforate, except occasionally 

 a minute pore near the aperture, and the high peristome is 

 continued around the aperture from the duplicate oral avicu- 

 larinm to the sides of the ooecium, the whole anterior part, 

 consisting of oral avicularia, peristome, and ooecium, stands 

 high and prominent above the remainder of the zooecium. 



Zooecia measure about 0.59 mm. long by 0.36 mm. wide, 

 and the aperture averages 0.125 mm. in width by 0.1 mm. in 

 length. 



The species shows resemblances to S. concinna in the pres- 

 ence of the lyrula, the form of the aperture, and the form, 

 size, and position of the primary oral avicularium. The cos- 

 tate border of the zooecium reminds one of Porella probos- 

 cidea Hincks, and there are also certain resemblances to 

 Porella {Phylact ella) peristomata Nordgaard. Because S. 

 concinna has been considered a very variable species, and be- 

 cause I originally listed this with concinna, I sent specimens 

 to Dr. Anna B. Hastings, of the British Museum, for compari- 

 son. Miss Hastings writes, ''we have a great variety of 

 specimens purporting to be concmna, some have more numer- 

 ous and regular marginal pores than the type, some have 

 mandibles with oblique sclerites, some have conspicuous fer- 

 tile zooecia, but none have these characters combined as in 

 yours and none have ribs between the marginal pores." 

 Therefore I feel that, even in a group that greatly needs 

 revision, I am fairly safe in describing this form as a new 

 species, and I have named it reduplicata on account of the 

 secondary oral avicularia of the fertile zooecia, which appear 

 in all of my material from Cape Cod to Labrador. 



