314 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 14 



reddish-brown ectocyst is removed the front is white, finely granulated 

 and perforated by funnel-shaped pores ; it is excessively thick. Proximal 

 to the aperture but not obscuring it is a low, rounded umbo which, in 

 younger stages, often bears a membranous area on its distal side, but 

 this area is nearly always closed off in complete calcification. Norman 

 noted the presence of a small, rounded avicularium low down near the 

 aperture, but this is usually rare and often wanting from whole colonies. 

 Levinsen found none in his Greenland material. 



The primary aperture is slightly more than a semicircle, the proximal 

 border nearly straight. The operculum has the form of the aperture, 

 slightly broadest at the straight proximal end, a pair of heavily chitinized 

 sclerites at the proximal corners for attachment, a moderately broad 

 bordering sclerite and on each side a somewhat fan-shaped one inside 

 from the border extending forward about two-thirds of the length of 

 the operculum with the muscle attachments at its tip. No cardelles; 

 no spines. The primary peristome is low and thin and is surrounded on 

 the lateral and distal sides and deeply immersed by a broad, heavy fold 

 of the frontal which may fuse with and obscure the primary peristome. 



The primary ovicell is hyperstomial, prominent, thin-walled with a 

 few pores, but very soon becomes covered with a thick layer like that 

 of the front, in addition to which the heavy lateral-oral ridges grow 

 around above the orifice and may unite to form a broad, low collar; in 

 complete calcification the ovicells are almost entirely submerged. 



Smitt may have been the first to record this species (from Spits- 

 bergen) if my interpretation of his figures (1871, plate 21, figs. 25, 26) 

 is correct; certainly they cannot refer to Lepralia megastoma Busk, 

 1857:55, which has an imperforate and costate frontal. Hincks had it 

 from the Gulf of St. Lawrence but considered it only a variety praeclara 

 of his Mucronella spinulifera; it is much like spinulifera in general ap- 

 pearance but totally different in fundamental characters since the latter 

 species has a simple operculum, an endozooecial ovicell and an imper- 

 forate frontal. Norman described it as Porella princeps, from west 

 Greenland, but in spite of the occasional suboral avicularium it cannot 

 be a Porella because of the porous frontal; moreover I have not been 

 able to discover any lateral connections of the avicularian chamber with 

 the areolar pores and presume that it is developed from the frontal pore 

 at the bottom of the chamber. Levinsen also recorded the species from 

 Greenland. 



Point Barrow, Alaska, 18 to 80 fms, numerous colonies on stones 

 and shells, G. E. MacGinitie, collector, Alaska Research Laboratory. 



