124 



separated into genera and which accordingly must provisionally be characterized 

 mainly in a negative way, I shall propose for these the name Heteroflustra, and 

 the introduction of such a provisional name seems to me necessary in all simi- 

 lar cases. 



Synopsis of the genera. 



1) The side- walls with multiporous rosette-plates; if ooecia are pre- 

 sent, they are egg-shaped, the distal wall forming at the same time a 

 distal and a proximal cup-shaped arch; 



2) the larvae are ejected through a chitinous tube, which opens 

 distally to the zooecial operculum, and may be covered by a movable, 

 calcareous valve; avicularia of the same size as the zooecia, lyriform; 



the operculum with two large wing-shaped lateral expansions. . . Sarsiflastra Jull.^ 



(S. abyssicola Sars). 



2) No such apparatus for the ejection of the larvae; egg-shaped v 

 ooecia may occur and smaller avicularia, the operculum of which has 



no lateral expansions Fhistra (L.) Lev. 



(Fl. foliacea, L. 



carbasea, Ellis and Sol.) 

 1) The side-walls have uniporous rosette-plates; if ocecia are pre- 

 sent, they are cup- or cap-shaped, the distal-wall only forming a single 

 arch: 



3) The ooecia immersed into tlie bottom of kenozooecia (no avicularia, 



colony with two-rowed branches) Kenella n. g. 



a (K. biseriata Busk.) 



3) Tlie ooecia immersed in ordinary zooecia or in avicularia (the 

 colonies with several rows). 



4) The distal wall, at any rate in the ooecia-bearing zooecia, very 

 often also in the ordinary zooecia, meets with the basal wall in an 

 angularly bent or curved line; the free edge of the ooecia on the frontal 

 side of the colony lies much lower than the basal edge; the avicularia 

 have the same size as the zooecia, (the colonies much branched dichoto- 

 mously, with frequently the branches meeting and thus forming an open 

 network; radical fibres occur in the angles of the branches) .... Retiflustra n. g. 



4) The distal wall horizontal or very slightly curved; the free, 



' 46, p. 43. 



