167 



cavity, but these two cavities are melted together in a single one in all these 

 forms, in which the polypide tube has a basal wall of its own. 



Synopsis of the families: 



1) Zocecia with calcareous spicula in the shape of compasses and 

 bows; ocecia with two calcareous layers, springing from the whole 

 anter of the aperture; the opesiulaj are always completely separated 

 from the aperture Thalamoporellidae n. f. 



1) Zooecia without spicula; if ooecia are present they have only a 

 single calcaieous layer (the endoocvclum) and are placed distally to the 

 aperture of the zott'cium, which is distinctly visible: 



2) No avicularia, no oo-cia, generally two forms of zoa>cia .. . Steganoporellidae. 

 2) Avicularia always and ooecia sometimes present; only a single 



form of zooecia Aspidostomidae. ' 



Family Steganoporellidae. 



The zooecia, which in most cases occur in double form, are always without 

 spines, but generally provided with pores. The frontal wall of the polypide-tube 

 is usually free, as the two opesiula; are generally not separated from the aperture 

 of the zott'cium. The operculum, which is sometimes bounded by a chitinous 

 sclerite proximallj', sometimes continued immediately into the frontal membrane, 

 is as a rule very large and then suspended by strong hinge-teeth. Each distal 

 wall with 2 and the distal half of each lateral wall with 1 — 3 multiporous ro- 

 sette-plates. No avicularia. No owcia. 



Synopsis of the genera. 



The whole of the calcified part of tlie frontal area lying proximally 

 to the aperture is a depressed cryptocyst; the aperture of the zowcium 

 is surrounded distally and laterally by a projecting margin; the zoa-cia 

 frequently occurring in two forms and provided with a large oi)er- 

 culum armed with teeth, which is suspended bj' strong hinge-teeth; 

 the polyjiide-tube is never continued proximally beneath the cryptocyst 

 cover Steganoporella Smilt. 



The proximal calcified part of the frontal wall is formed by a 

 larger or smaller, arched gymnocyst; the aperture is not surrounded 

 by a projecting margin; the zooecia occuiring only in single form 



' This family has been put up by F. Canu (1 1 b, p. 276). 



