14 



calcareous band in Fl biseriata, begins a little below the upper edge of the ver- 

 tical wall of the zooecia. This Cryptocyst reaches a somewhat greater develop- 

 ment in Fl. cribriformis and Fl. Schenaui (PI. 1, fig. 7 a, 7 c), in which it shows 

 a varying number of lines of growth, according lo the age of the zooecium. We 

 may mention finally, that while the zocecia in the free part of Fl. foliacea have 

 no Cryptocyst, such is rather highly developed in the incrusting part of the col- 

 lony and also, that it is well-developed in the avicularia of this species. 



Of the forms which we have here classed to the family Farciminariidae, the frontal 

 wall of most of them has neither a Gymnocyst nor a Cryptocyst, or there is only 

 a faint trace of the last. On the other hand both of them appear rather well-developed 

 in Farciminaria appendiciilata (PI. 1, fig. 11) and in Nellia tenella (PI. 1, fig. 13). 

 Within the family Bicellariidae we find a completely membranous frontal wall in 

 most of the species referred to the genera Buskia, Beania and Diachoris. The 

 Gymnocyst reaches its greatest development in Dimetopia and Bicellaria, because 

 it may here attain more than half the length of the zooecium (PI. IV, fig. 5 and 8), 

 while it only has a small extension in most of the Bagula species. With excep- 

 tion of Bicellaria grandis (PI. IV, fig. 5 a), in which species we find a large distally 

 freely projecting Cryptocyst lamina, I have not been able to find any trace of a 

 Cryptocyst in any other Bicellaria; still it seems as if a slightly developed Cryp- 

 tocyst can be found in almost all other members of the family, at least in the 

 older zocecia, in which it often seems to be represented by the proximal part, 

 which shows distinct lines of growth. The whole of the Cryptocyst shows distinct 

 lines of growth in the figure of the zooecium of Maplestonia simplex shown in 

 PI. IV, fig. 9 a, but the proximal part is only slightly developed. With exception 

 of the Flustra-hke Hoplitella armata (PI. II, fig. 10 a), in which the whole of the 

 frontal wall is membranous, a larger or smaller part of this wall is calcified in the 

 rest of the members of the family Scrupocellaviidce, and they have as rule a Gymnocyst 

 as well as a rugged or grained Cryptocyst, which in Celhilaria ornata even seems 

 to form the whole of the calcified part of the frontal wall. The Gymnocyst 

 however forms most frequently the major part of this wall, and its proximal part 

 in Menipea aculeata and Men. clausa attains nearly the two-thirds of the length of the 

 zooecium. The Cryptocyst seems to be strongly developed in most of the Caberea 

 species. While the whole calcified part of the zooecium in the Aeteidae is formed by 

 a Gymnocyst, the conditions are very variable within the large family Membrani- 

 poridae. While the whole frontal wall is formed by membrane in Membranipora 

 membranacea and related species, a larger or smaller part of it is calcified in 

 most of the remaining forms, and this calcification is sometimes represented 

 only by a Gymnocyst, sometimes only by a Cryptocyst and sometimes by both. 



