262 University of California Publications in Zoology, [^oi^- 4 



rather narrow (pi. 14, fig. 5). In the matrix in which the zooecia 

 are imbedded, two triangular hollow spaces, tri. spa., just below 

 the aperture of each zooecinm. Ooecia none. 



This species is quite abundant on our southern coast, having 

 been obtained at various points near San Pedro and San Diego, 

 California. Also found less abundantly at Kadiak, and Orca, 

 Prince Williams Sound, Alaska. 



39. Membranipora occultata sp. nov. 



PL 14, figs. 6, 7, 8, 9. 

 Membranipora unicornis, Kobertson, 1900, p. 324. 



Zoarimn incrusting, forming a somewhat delicate lace work 

 closely adhering to the substratum. Zoa'cia alternate, elongated ; 

 aperture oval, occupying from two-thirds to three-fourths of the 

 front ; operculum rather broad, not semi-circular ; margin raised, 

 calcareous, slightly crenate on the inner edge ; on each side of the 

 lower half of the aperture a spine, sometimes stiff (pi. 14, fig. 6, 

 st. sp.) and outstanding, sometimes flexible (fig. 7, /?. sp.) and 

 inclined over the aperture; often but one spine (fig. 6) which is 

 then usually stiff and projecting outward; on the lower third or 

 fourth of the zooecial wall just below the aperture, an avicularium 

 (figs. 6 or 7 av.) with elongated beak, its tip much raised and 

 directed obliquely upward, or infrequently downward ; scattered 

 irregularly through the zoarium a few spatulate avicularia (fig. 

 8) with rounded mandible directed upward. Ooecia (fig. 7, oe.) 

 small, membranous, or very slightly calcareous ; almost complete- 

 ly covered, as by a hood, with the calcareous wall (fig. 9, cal. wa.) 

 of the lower part of the distal zooecium, behind which the ocecium, 

 oe., is hidden; the wall, cal. wa., not uniting with the proximal 

 edge of the ocecial wall but standing out leaving a considerable 

 space between it and the ooecial wall; surmounted by an avicu- 

 larium, av., with long tapering mandible whose tip is raised and 

 frequently covering the lower rim of the aperture of the distal 

 zooecium. 



The most characteristic mark of this species is the submersion 

 of the ocecium under the wall of the distal zooecium, which thus 

 hides it more or less completely as behind a stiffened veil. The 



