29 
must suppose there bas been a cbitinous operculum. In Melicer- 
tites Royana Waters bas found tbe closure consistiiig' of tbree 
(two superior and one inferior), rarelj four calcareous growtbs 
starting from tbe margin and uniting in tbe centre and as above 
mentioned tbe orifice is closed in a similar manner in tbe species 
of Caloporella, only tbat tbe tbree growtbs have a somewbat diffe- 
rent position. 
Wbile tbe Eleidae are provided with opercula and avicularia 
tbey lack ooecia but bave sometimes gonozooecia of tbe same 
structure as tbose found in some Cyclostomata. As fiirtber tbe 
form, tbe structure and tbe mode of combination of tbeir zooecia 
are cyclostomatous 1 cannot doubt that tbey are nearly related to 
tbe Cyclostomata. Tberefore I agree witb Gregory^) in conside- 
ring tbe presence of avicularia (as also of opercula) as a case of 
parallel development. Besides, tbese avicularia do not quite agree 
witb those found in tbe Cheilostomata. Wbile tbe latter are al- 
ways provided with a membranous area (tbe subopercular area), 
seated behind tbe operculum and separated from tbe opercular area 
eitber by a calcareous cross-bar, or only partially by tbe binge- 
teetb of tbe operculum, a sucb subopercular area bas not been de- 
veloped in tbe avicularium of tbe Eleidae in wbicb of course tbe 
operculum or mandible has fllled tbe wbole aperture, consequently 
terminated by a straigbt posterior margin. 
As to tbe Ceidae, Gregory^) considers tbat tbe Bryozoa 
referred to this division are only specimens of different species of 
Eleidae wbicb bave lost tbeir front wall. Gregory, bowever, is 
not right in bis supposition. In most Cyclostomata we can in eacb 
zooecium distinguisb two different portions of tbe front wall for- 
ming obtuse angles with one anotber, an inferior portion bidden 
in tbe interior of tbe colony and a superior superficial portion 
Op. cit. pag. 49. 
*) Catalogue of oretaceous Bryozoa, Vol. 1, pag. 288. 
0 Op. cit. pag. 291. 
