162 



attained the correspondence in form of aperture and structure of operculum 

 that we have just pointed out. 



Micropora Gray. 



(PI. VIII). 



The two opesiulse, which are more or less constant, have the form of simple 

 perforations. Spines may appear. The ocecia, which have a membranous ecto- 

 ocecium, are endozocecial but very prominent, and the small avicularia, which 

 are situated proximally to the aperture, are furnished with a complete cross- 

 bar. Pore-chambers with few pores. 



To this genus belong M. coriacea Esper, M. perforata Mac Gill. (PI. VIII, fig. 4 a) 

 and a species which has hitherto been confounded with M. coriacea, and for which 

 I will propose the name M. Normani^ (PI. VIII, figs. 3 a— 3 b). Of this species I 

 have only seen a little fragment from Hastings, sent me by the late Mr. Peal, and 

 having lost it I shall only mention, that the operculum is calcareous and that 

 the distal half of the endoocecium lacks that cryptocyst cover, ending in an 

 angular margin, which is found in M. coriacea. 



Microporina n. g. 



The two opesiulse, which however are sometimes filled up, appear as simple 

 perforations. Numerous pores. No ooecia, but avicularia with cross-bar occur. 

 Each distal wall and the distal half of each lateral wall with a row (6 — 8) of 

 one- or two-pored rosette-plates. A longitudinal series of parietal muscles is placed 

 on each side between the cryptocyst and tlje covering membrane. Cellaria borealis 

 Busk and Micropora elongata Hincks belong to this genus. 



Macropora M. Gilliv., char, emend. 



The zooecia very thick-walled, provided with pores but without spines and 

 without opesiulse. The zooecial aperture is provided with a well-developed vesti- 

 bular arch. Oa;cia and ordinary avicularia wanting, but among the zooecia we 

 find some which have an aperture of a very different form and whose distal 

 margin is furnished with three membranous, feeler-like filaments. Pore-chambers. 



'■ 56, p. 7, note. 



