FROM THE LOYALTY ISLES, NEW GUINEA AND NEW BRITAIN. 445 



occurrence of two kinds of zooecia. The one kind possesses opercula of an ordinary 

 form and are without spines ; the other are characterised by large lobed opercula 

 and by the presence of spines in the bays between the lobes and on the sides of 

 the orifice. In one zooecium there is a slight undulation in the operculum below 

 the lateral spine so that this also lies in a bay ; this seems to suggest that the 

 bays may be due to a retardation of growth produced by the presence of spines. 



No reason can at present be suggested for the existence of these two kinds of 

 opercula. The zooecia contain similar polypides ; those with the lobed operculum 

 possess slightly stronger opercular muscles. 



20. Monoporella spinifera, n. sp. PI. XLII., fig. 4. 

 There are two small pieces. 



Zooarium encrusting. Zooecia hexagonal, separated by depressed lines ; surface 

 covered with large poi-es ; the intervening parts studded with minute nodules ; orifice 

 horse-shoe shaped, surmounted by ten short brown spines. 



Operculum calcareous, covered with a brown chitinous membrane ; horse-shoe 

 shaped within the orifice, the distal wall of the zooecium raised into a shelf projecting 

 into the cavity, the remaining space being closed in by a membranous diaphragm. 

 There is one peculiar zooecium in which the diaphragm is calcified, two small holes 

 being left for the opercular muscles. In this zooecium the orifice is drawn out into 

 lobes between the spines. 



Ooecia ? 



Measurements: zooecium l'2mm. in length xl'lSmm. in width; operculum ■27 mm. 

 in length x '32 mm. in width. 



21. Schizoporella biaperta, Michelin. Hincks, Brit. ilar. Pol. p. 25-5. 

 Fairly abundant. 



22. Schizoporella torquata, Quoy and Gaimard. 

 Only one fragment. 



23. Schizoporella triangula, Hincks. PL XLII., fig. 5. Hincks, Ann. Mag. Nat. Hist. 

 (5) VIII. p. 12, 1881. Waters, Ann. Mag. Nat. Hist. (5) XX. 1887, p. 191. 



The single specimen from New Britain seems on the whole to resemble Hincks' 

 species, though it dififers from it in some particulars. The surface is generally 

 reticulo-punctate without nodules, except in some old zooecia where small nodules are 

 found. The a\'icularia are placed on a small circular elevation from which lines pass 

 to the sides of the orifice marking out a distinct raised area. These avicularia are 

 not elongate but small and circular with a rounded mandible. However the form in 

 this species seems to var}' as in a specimen from Port Western, Melbourne, some 

 avicularia are elongated while those on adjacent zooecia are rounded. The ooecium 

 has a rough punctured surface, the older cells possessing also small nodules. The pro- 

 jecting processes and teeth on the margin of the ovicell described in Hincks' species 

 are absent. 



27. Schizoporella depressa, n. sp. PI. XLII., fig. 6 and 6a. 



Zoarium encrusting. Young zooecia ovate with a smooth surface; later the wall 



at some little distance from the orifice becomes thickened so that eventually the 

 w. IV. 60 



