INTKODUCTION. 
XXVll 
Section 1. C. 0 per culls. Operculum present. Fam., Eleid^n 
and Myriozoumidae. 
Section 2. C. Faseiculines. Zooecia inoperculate. Zoarium 
formed of bundles of zooecia. Fam., Fascigeridge and 
Fasciporidae. 
Section 3. C, Tuhulines. Zooecia inoperculate. Zoarium 
variable in form, tbe zooecia being arranged irregularly, 
radially, or in linear series. Fam., Tubigeridae, Sparsidge, 
Clausidae, Crisinidae, and Caveidae. 
Section 4. C. Foramines. Zooecia inoperculate. Zoarium 
“excessively variable” in form. Peristomes not projecting 
above the surface of the zoarium. Fam., Ceidae, Cavidae, 
Cytisidae, Crescisidae. 
D’Orbigny’s order the Cellulines is practically the same as the 
Cheilostomata, for the M^u’iozoumidae are the only Centrifuginh 
which are unanimously regarded as Cheilostomes. His Centrifugines 
therefore included almost all the Cyclostomata, but unfortunately 
he scattered among its families many Ctenostomata and Palaeozoic 
Bryozoa. Thus Fenestella^ Ichthyorachis, Penyiiretepora, 2 iH(\.Polypora 
were all included in the Sparsidae ; the Silurian Omniretepora 
was placed among the Crescisidae, and the Ctenostomata Amathia^ 
Serialaria, Valkerta, etc., in the Serialaridae. 
Many, therefore, of d’Orbigny’s families have been regarded as 
so artificial that the whole scheme has been often rejected without 
recognition of its large measure of truth. 
D’Orbigny’s first suborder, the C. PadicelUs, has to be abandoned, 
as it included two distinct families allied only by the method of 
attachment ; the Serialaridae are Ctenostomes and the Crisidae are 
Busk’s Cyclostomata Articulata. 
The C. Empdtes are the Cyclostomata Inarticulata of Busk ; but 
this suborder of d’Orbigny’s includes many Palaeozoic genera 
which have to be removed. Of its four sections the OpercuUs 
includes a family of Cheilostomata or a group intermediate between 
Cyclostomata and Cheilostomata. The two sections, Fasciculinh 
and Tubulines, exclusive of various Palaeozoic genera are the 
Cyclostomata Inarticulata, and the Foraminls practically represent 
the Cretaceous Trepostomata. 
D’Orbigny’s Orders and most of his suborders are therefore still 
recognized as natural groups. 
