290 MOLLUSCOIDEA—BRYOZOA SUB-KINGDOM V 
Family 13. Celleporidae. Busk. 
Zoecia urceolate, more or less erect, and irregularly crowded together ; often forming several 
or many superimposed layers. Tertiary and 
Recent. 
Cellepora, Fabricius emend. Busk 
(Spongites, Oken ; Celleporaria, Lamx.), (Fig. 
488). Zoarium multiform, encrusting, or 
erect and ramose. Zoccia in the older 
portions more or less erect and very irreg- 
ularly disposed. Orifice terminal, entire, or 
sinuated, with or without internal denticles ; 
in connection with it are usually one or 
more rostra bearing avicularia. Inter- 
calated avicularia generally present also. 
Fic. 488. The surface of weathered specimens dotted 
Cellepora _conglomerata, Goldf. Oligocene; by the unequal apertures of vesicle - like 
Astrupp, near Osnabriick. A, Zoarium, 1/). . : ; 
B, Upper surface, enlarged. ; cells. Tertiary and Recent. 

Range and Distribution of the Bryozoa. 
The class Bryozoa begins in the Ordovician, and is represented continuously up 
to the present time. The older Palaeozoic forms belong chiefly to two sub-orders— 
the Cyclostomata and Trepostomata. 
A considerable number of Cyclostomatous genera are present in the Ordovician, 
all of them being closely related with Mesozoic and recent types; but throughout the 
remainder of the Palaeozoic, and in the Trias also, the sub-order is very sparingly 
represented (if we except the somewhat doubtful Ceramoporidae and Fistuliporidae), 
and in some parts quite absent. In the Jura and Cretaceous, however, a remarkable 
increase took place, hundreds of species being known from these formations, During 
the Tertiary their strength was again materially reduced, and the living Cyclostomata 
barely exceed 100 species in number. 
The Trepostomata appear suddenly and in great variety in the Ordovician, from 
which over 200 species are known, but entered almost immediately upon a period of 
decline. From the Trenton and Cincinnati groups alone more species have been described 
than from all of the later Palaeozoic formations put together. There is at present no 
evidence to show that the group survived later than the Palaeozoic era, but it is not 
unlikely that their descendants may be found among certain Mesozoic families, such 
as the Ceidae and Meliceritidae, which are provisionally assigned to the Cyclo- 
stomata. 
The Cryptostomata are likewise confined to rocks of Palaeozoic age, but, as has 
been remarked above, may be very confidently regarded as the forerunners of the 
Chilostomata. 'True members of the latter group are first met with in the Jura, but 
they develop rapidly, and from the Cretaceous onward remain the dominant type. 
The Triassic and Liassic Bryozoans belong chiefly to the Cerioporidae. This 
family, together with the Dviastoporidae, Fascigeridae, and other members of the 
Cyclostomata, are abundantly represented in the Middle Jura of Lorraine, Southern 
Germany, England, and Normandy. The Upper Jura, on the contrary, yields com- 
paratively few Bryozoan fossils. 
The Cyclostomata still predominate in the Neocomian and Gault, but in the 
Cenomanian a number of Chilostomatous genera make their appearance. The fauna 
