THE MOUNT DESERT REGION 343 



There is a row of marginal pores between the ribs. The oral 

 aperture is large, unsymmetrically oval, with occasionally a 

 small denticle on the middle of the proximal border, though 

 this is usually lacking. A small oval avicularium is situated 

 at one side and partially beneath the rostrum. Larger avicu- 

 laria of the same general form are scattered irregularly over 

 the zoarium. Ooecia are hemispherical, wide open toward the 

 aperture, and irregularly perforated. 



Rhamphostomella costata Lorenz, 1886. PI. 10, fig. 7. (Os- 

 Inirn, 1912, p. 244, references and synonymy; 1912 a, p. 286, 

 records for Labrador and Nova Scotia; Whiteaves, 1901, p. 

 108, 'abundant among St. Lawrence dredgings.') Very com- 

 mon on stones and Pyura stems on hard bottom. Dredged at 

 thirty-three stations, not found at shore stations. In my 

 experience, this is by far the most common member of the 

 genus on the American coast north of Cape Cod. It often 

 forms heavy incrustations on coarser stems. Like the other 

 species of this genus here listed, it is high northern in range, 

 Franz Josef Land to Greenland and south to Cape Cod. 



There appears to be some question whether costata should 

 be considered a distinct species or a variety of scahra. At any 

 rate, the true costata has a very prominent pointed rostrum, 

 with the strong frontal ribs of the zooecium contined upon it 

 to near its tip; the suboral avicularia are larger and bluntly 

 pointed, as are also the frontal avicularia. The upper surface 

 of the large hemispherical ooecium is coarsely and irregularly 

 perforated. The oral denticle is large and irregular. 



Occasional specimens show the character of the variety 

 cristata, with a transverse bar across the tip of the rostrum. 



Rhamphostomella BrLAMiNATA (Hincks), 1877. PL 10, fig. 

 8. (Osburn, 1912, p. 244, synonymy and references; "WTiit- 

 eaves, 1901, p. 108, Canadian records.) Common on stones 

 and Pyura stems, from hard bottom ; not taken at shore sta- 

 tions, but dredged at twenty-five stations. Spitzbergen to 

 Greenland and along the North American coast to south of 

 Cape Cod. Of all the members of the genus here recorded 

 it is the only one that extends into the more temperate waters 



