Polyzoa of Queen Charlotte Islands. 13 



the ridges between them slightly raised, usually bearing several 

 elliptical pores ; orifice arched above, straight below, much 

 broader than high, on each side a stout bifid spine (occasionally 

 simple) ; peristome much thickened in front and rising into a 

 central mucro. Avicularia none. Ocecium large (covering 

 about half the cell above it) , rounded, taller than broad, de- 

 pressed in front, with a shallow oral arch ; surface smooth, 

 rather thickly punctured, the forked spines showing in front 

 of it. 



Loc. Cumshewa ; Houston Stewart Channel ; common. 



The furcate spine is often wanting, especially in the older 

 cells. 



Crihrilina Mppocrejns^ n. sp. (PI. XX. figs. 6, 6 a.) 



Zocecia ovate, quincuncial ; surface lustrous, flattish (sutures 

 very shallow), traversed by ladiating ridges (from three to five 

 on each side), which pass from the sides to the centre (no 

 median keel), the grooves between them occupied by a line 

 of rather large oblong pores ; at the origin of each ridge an 

 elliptical foramen, covered in by a delicate membrane ; orifice 

 large, well arched above, constricted a little above the lower 

 margin, which is straight ; operculum of a rich reddish brown ; 

 peristome not elevated, lower margin much thickened, usually 

 terminating on each side in a knob ; large, elongate, depressed 

 spatulate avicularia scattered amongst the cells. Ooecium (?). 



Surface of zoarium very flat ; colour brown, with a tinge 

 of red ; in old states white and highly calcified. 



Primary cell ovate, area occupying about three fourths of 

 the front surface, with a membranous covering ; margin slightly 

 thickened ; about fourteen spines surrounding the area, which 

 originate outside and a little below the margin. 



Log. Cumshewa ; Houston Stewart Channel ; abundant. 



The primary cell is interesting as giving a clue to the 

 genetic history of the species and of the Cribriline form gene- 

 rally. There can be little doubt that the ridges which con- 

 stitute the chief framework of the front wall in the adult are 

 modifications of the spines, which are preserved in the early 

 condition of the cell. 



EXPLANATION OF THE PLATES. 



Plate XIX, 



Fig. 1. Scrnpocellaria varians, n. sp., nat. size. 1 a. ZocBcia, magnified. 



1 h. Dorsal surface. 1 c. Avicularia. _ 

 Fig. 2. Membranipora nigrans. 2 a. Large avicularium. 

 Fig. 3. Memhranipora protecta, u. sp. 



