290 



MOLLUSCOIDEA BRYOZOA 



SUB- KINGDOM V 



Family 13. Celleporidae. Busk. 



Zocecia 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 ; Cetteporcvria, Lamx.), (Fig. 

 488). Zoarium multiform, encrusting, or 

 erect and ramose. Zocecia 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. 

 The surface of weathered specimens dotted 

 by the unequal apertures of vesicle - like 

 cells. Tertiary and Recent. 



FIG. 488. 

 Cellepora conglomerata, Goldf. 



Astrupp, near Osnabrtick. 

 B, Upper surface, enlarged. 



Oligocene : 

 A, Zoarium, 1/1- 



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 Cydostomatous 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 Geramoporidae 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 Oyclostomata 

 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 Geidae 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 Diastoporidae, 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 



