29 
must suppose there has been a chitinous operculum. In Melicer- 
tites Royana Waters!) has found the closure consisting of three 
(two superior and one inferior), rarely four calcareous growths 
starting from the margin and uniting in the centre and as above 
mentioned the orifice is closed. in a similar manner in the species 
of Caloporella, only that the three growths have a somewhat diffe- 
rent position. 
While the Eleidae are provided with opercula and avicularia 
they lack ocecia but have sometimes gonozooecia of the same 
structure as those found in some Cyclostomata. As further the 
form, the structure and the mode of combination of their zooecia 
are cyclostomatous I cannot doubt that they are nearly related to 
the Cyclostomata. Therefore I agree with Gregory”) in conside- 
ring the presence of avicularia (as also of opercula) as a case of 
parallel development. Besides, these avicularia do not quite agree 
with those found in the Cheilostomata. While the latter are al- 
ways provided with a membranous area (the subopercular area), 
seated behind the operculum and separated from the opercular area 
either by a calcareous cross-bar, or only partially by the hinge- 
teeth of the operculum, a such subopercular area has not been de- 
veloped in the avicularium of the Eleidae in which of course the 
operculum or mandible has filled the whole aperture, consequently 
terminated by a straight posterior margin. 
As to the Ceidae, Gregory?) .considers that the Bryozoa 
referred to this division are only specimens of different species of 
Eleidae which have lost their front wall. Gregory, however, is 
not right in his supposition. In most Cyclostomata we can in each 
Zzooecium distinguish two. different portions of the front wall for- 
ming obtuse angles with one another, an inferior portion hidden 
in the interior of the colony and a superior superficial portion 
1) Op. cit. pag. 49. 
?) Catalogue of eretaceous Bryozoa, Vol. 1, pag. 288. 
") Op. cit. pag. 291. 
