BRYOZOA. 291 



the surface of the zoarium in which the embryoes are developed, 

 or a special receptacle which is attached to the zooecium and 

 serves the same purpose. 



DIAPHRAGMS (=ttibul& and septa auctt.): The straight plates 

 which cross the tubular zocecia and mesopores in the TREPO- 

 STOMATA. 



CYSTIPHRAGMS: The convex plates which line the walls of the 

 zooecia in some of the TREPOSTOMATA. 



OPERCULA or PERFORATED DIAPHRAGMS: Horizontal plates, 

 perforated su been t rally, closing the mouths of the zooecia. As 

 growth proceeds in the colony these are left behind in the tubes 

 and mark the successive stages. 



SUPERIOR HEMI-SEPTUM: A plate or laminar projection which 

 forms the posterior border of the primitive zooecial aperture, 

 in the typical CRYPTOSTOMATA. 



INFERIOR HEMI-SEPTUM: A small plate often present in the 

 CRYPTOSTOMATA, springing from the anterior wall or the medium 

 laminae of double leaved forms, at a point a short distance 

 below the "Superior hemi-septum". 



LUNARIUM: A more or less thickened portion of the posterior 

 wall in mam* Bryozoa which is curved to a shorter radius and 

 usually projects above the plane of the zooec-ium aperture. It is 

 of crescentic form, and represents the "notch" which is such a 

 characteristic feature of the aperture of some of the recent 

 CHEILOSTOMATA. In the Palaeozoic Bryozoa it is variously modi- 

 fied and drawn out trough-like. 



PRIMARY APERTURE: "The original orifice" of the zooecium in 

 the CRYPTOSTOMATA. 



SECONDARY or SUPERFICIAL APERTURE: The superficial orifice 

 of the tubular prolongation of the original aperture. 



OBVERSE and REVERSE: Two terms employed to designate, 

 respectively, the celluliferous and non-celluliferous faces of the 

 zoaria of the FENESTELLID.E, ACAXTHOCLADIID.E, and PHYLLOPO- 



RINID.E. 



DISSEPIMENTS: Short non-celluliferous bars connecting the cell- 

 bearing branches in the FENESTELLID.E, and developed at regu- 

 lar intervals. The rounded, hexagonal or quadrate meshes of 

 the net work thus formed are known as the "fenestrules". 



