444 REPORT OX THE POLYZOA COLLECTED BY DR WILLEY 



the tip ; the horizontal limb is also deeply bifurcated and each branch so formed 

 divides twice. 



In some of the more central zooecia, some of the branches have met across the 

 area; the fusion has however not progressed so far as in the typical Hiantopora 

 ferox, MacGillivray, (Membranipora radicifera var. ferox, Kirkpatrick) so that here 

 we have an intermediate stage between the two varieties " intermedia " and "ferox." 



15. Membranipora irregularis, d'Orbigny. 



D'Orbigny, Voyage dans I'Amer. M^rid. viii. 56. 



This is fairly abundant, growing round Echinid spines. 



17. Membranipora punctigera, Hincks. Ann. Mag. Nat. Hist. 5. Vlll. 18S1, p. 4. 

 One colony growing on a Nautilus shell. No ooecia present. 



19. Monoporella polymorpha, n. sp. PI. XLII., figs. 3 and 3 a. 



Zoarium encrusting. Zooecia large, roughly hexagonal in shape, convex, rising 

 slightly towards the orifice, separated by distinct lines ; the surface in young cells 

 covered with large opaque dots, these being obscured later by the growth of a 

 brownish cuticular epitheca ; below the orifice a little brown patch. 



Measurements of zooecia 1"07 mm. to 1"34 mm. in length x '86 mm. to 1'12 mm 

 in width. 



Opercula calcareous, covered by a chitiuous membrane. 



Opercula of two kinds : 



(1) the form occurring most frequently; arched above with a straight lower 

 margin ; bordered by a dark line, the greater part of the operculum being coloured 

 brown leaving a light rim above. 



Measurements : -3 to •34 mm. in width x -26 to '28 mm. in length. 



(2) not quite so numerous as the first ; sides of the operculum sloping out- 

 wards from the straight lower margin ; upper border drawn out into three lobes ; 

 here also a semi-circular brown patch occupying the larger part of the operculum. 



Measurements : Width at base of operculum from '3 to "So mm. 



„ top „ „ '42 to '43 mm. 



Length „ „ -32 to '39 mm. 



In the bays between the lobes of the operculum and also on the sides just 

 below the lateral lobes are little circular scai's, showing the presence of spines absent 

 on zooecia bearing ordinary opercula. Rosette plates unusually large. Ooecium conical, 

 with well marked ridges and deep grooves alternately radiating from the apex ; from 

 four to six indentations on the floor of each groove. Operculum of the fertile cell 

 being of the more ordinary form, the upper margin arched, the lower straight or 

 slightly curved inwards. 



Measurements of ooecium 96 mm. in width x -93 mm. in length. 



This is a remarkable species being noticeable on account of its size and of the 



