„, , ., ,. , BEYOZOA. 1 1 1 



Distribution.! 



with Worthenopora, belonging to the Chilostomata, are new types. Among the Trepo- 

 stomata, the FistuUporidce are abundant, and Stenopora, Leioclema, Anisotrypa, and 

 Batostomella not uncommon. Both the Cyclostomata and Ctenostomata are poorly- 

 represented, each by one or two insignificant species. 



Carboniferous System : The rocks of this age are mostly unfavorable for the 

 preservation of the Bryozoa, and only a few localities are known in this country 

 where good specimens may be obtained. With the exception of Stenopora and Fistu- 

 lipora all the observed forms belong to the cryptostomatous genera Fenestelta, 

 Polypora, Thamniscus, Acanthocladia, Pinnatopora, Septopora, Diplopora, Sphragiopora, 

 Chainodidyon, Prismopora, Cystodictya, and Rhombopora. 



In America Bryozoa are rare or entirely unknown in the strata above the paleo- 

 zoic. Vost of the species known are from the Cretaceous and Tertiary rocks of New 

 Jersey, Mississippi and Arkansas. In Europe the Triassic system is equally poor in 

 Bryozoa, but in the Jurassic they are represented by nearly eighty species, most of 

 them Cyclostomata. This suborder continues to be almost exclusively represented to 

 the Cenomanian in which the Chilostomata are present, though not yet in very great 

 numbers. Even in the Upper Cretaceous, from which d'Orbigny mentions 662 species, 

 the Cyclostomata and Treposlomata are nearly twice as numerous as the Chilostomata. 

 In the Tertiary rocks the Cyclostomata have become less numerous and the Chil- 

 ostomata more abundant, the ratio of representatioa at the close of the age being 

 approximately like the present. 



