EXPÉDITION ANTARCTIQUE BELGE 



and the position in the zoœcium. Whenever possible the oral aperture should be examined 

 from the inside, and the position of any denticles to which the opercula are attachcd should 

 be noticed. Some of the présent inconsistencies would hâve been removed if closer attention 

 had been given to the various characters of the opercula ; but while urging that more study 

 should be given to thèse chitinous structures, I a m not maintaining that it is a character 

 upon which the largest groupings can be based. 



The genus Lagenipora, as extended by me, will show the value of the opercula, for 

 hère, throughout the group, the operculum is of nearly the same size and shape, with the 

 muscular dots in the same position. This genus has throughout similar and characteristic 

 ovicells, thus showing by the two characters a natural group, and proving the value of the 

 characters. There are many cases in which the relationship has first been indicated by the 

 opercula; and in species where other structures vary much in size and with âge, the opercula, 

 will as a rule, be found quite similar throughout a colony. 



Caution is at présent required, lest various authors taking différent characters, should 

 create such an unwieldy number of gênera, that the study of the Bryozoa is thereby thrown 

 back for a time. 



A work like the présent is not suitable for introducing new ideas of gênerai classification, 

 and often generic names hâve to be used about which there is much doubt, and where 

 modifications are expected ; but in employing names now accepted it is believed, that the 

 species will be readily recognised, however much the gênera may be shufned. The classification 

 of the Cheilostomata is based upon a more solid foundation than that of the Cyclostomata, 

 as so many more characters are used, and we hâve no reason to expect the changes to be 

 universal, although some gênera may be dropped and others modified. 



Distribution 



The number of gênera now recorded from the Antarctic is greater than from the Arctic ; 

 and further, many more gênera are known from the southern hémisphère than from the 

 northern in fact there are but very few northern gênera not represented in the southern 

 hémisphère, whereas a considérable number from the south are not known north of the 

 equator. Gcmellaria known in Arctic seas is not found in the Antarctic. Pseudoflustra has a 

 close ally ; Rhamphostomella has not been found, but we are not sure about this being a satis- 

 factory genus ; no spécimen of the cosmopolitan Crisia has yet corne from the Antarctic, but 

 it is common in the Subantarctic and we ma}' expect it to be found. 



From the Antarctic, but not known in the Arctic there is Catenicella, Turritigera, 

 Bifaxaria, Beania (which however occurs in northern seas), Systenopora gen. nov., Cellarinella 

 gen. nov., Chapcria, Heteropora ('). 



Having recently worked upon Arctic Bryozoa ( 2 ), old friends were looked for, and one 

 of the most interesting forms is Megapora hyalina nov. most closely related to M. ringens 

 Bush, onlv known from Shetland and Bergen ; Scmpocellaria antarctica nov. is the represen- 



fi) Other gênera known in the southern hémisphère only are Bipora, Calpidium, Calwellia, Claviporella, Didymia, 

 Dimetopia, Diplacium, Euthyris, Farcimia, Foveolaria, Haswellia ?, Ichthyaria, Inversiula, Lunulites, Petralia, Scknaria, 

 Thairopora, Thalamoporclla, Urceolipora, Rhabdozoum, Caleschara, Aspidostoma. 



(2) Bryozoa from Franz Josef Land. (Litui. Sec. Journ. Zoo!., vol. XXVIII, p. 43-io5). 



