on the PoJyzoa^ 161 



form of structure^ and should be recognized as such in our 

 system. 



Busk (in the ' Challenger ' Report) has included in the 

 present family Micropora, Bteganoiiorella^ and a genus Vincu- 

 laria, of which a cylindrical habit of growth is an essential 

 character, and which in other respects is represented as being 

 somewhat intermediate between Micropora and Steganopo- 

 reUa, The peculiar habit of growth (as Mr. Busk has else- 

 where virtually admitted) is of no account whatever as an 

 indication of affinity ; and it would probably be better that 

 such a name as Vincularia^ which inevitably suggests cylin- 

 drical form, and little but this, should disajj))ear from our 

 nomenclature, Vincularia gotkica of the ' Report ' is furnished 

 with the " double ectocyst," and will probably find a place in 

 the same family as Sieganoporella and its allies. 



In the family of the Microporidse such forms only must be 

 included as agree in general structure with the well-known 

 and widely distributed Micropora coriacea^ Esper. 



Fam. char. — Zooecia with raised margins ; front wall 

 depressed, wholly calcified ; orifice enclosed by a calcareous 

 border, operculum with a distinct hinge. 



The species of l^licropoia are invested by a membranous 

 ej)itheca, which seems to be composed of comparatively stout 

 and durable material, and is more persistent than is usual 

 amongst the Poly^oa. A characteristic feature is the foramen 

 on each side of the front wall a little below the orifice. 



Amongst the forms which are furnished with the " double 

 ectocyst " (some of which have hitherto ranked amongst the 

 Microporid^) are the species comprised in the genus Stegano- 

 porella^ Smitt, Memhranipora antiqua, Busk, and one or two 

 kindred species described by Juilien, Vincularia ahyssicola, 

 Smitt, Caleschara denticulata, MacG., and Diplopora cincta^ 

 Hutton. In all these forms the front wall of the cell is 

 simply membranous ; it carries the oral opening and the oper- 

 culum. At a greater or less distance below this membranous 

 covering a calcareous lamina is interposed, which divides the 

 cavity of the cell into two compartments, an upper and an 

 under ; the lower or aboral chamber contains the polypide, the 

 use of the upper has not been determined. At the upper end 

 of the calcareous lamina there is a large opening {ppesia of 

 Juilien) by means of which the two chambers are brought into 

 communication and through which the polypide finds access 

 to the orifice of the cell. Theopesiais always of much larger 

 size than the orifice and variable in shape. 



The species characterized by the structure just described 

 may rank as a single family, to which it is }»robably right 

 that the name Steganoporellid(je should be assigned, Smitt 

 Ann. ct" Mag. N. Hist. Ser. 5. Vol. xix. 11 



