BRYOZOA. 341 



have not met with any species having the characters ascribed 

 to the genus by its author. The others are distinguished by 

 easily recognized structural peculiarities and corresponding 

 zoarial features. Leioclema, now referred with some doubt to the 

 next family, may prove to have closer affinities with Tremato- 

 pora than I am at present disposed to admit. 



(5) BATOSTOMELLID.E. The zoaria of this family vary ex- 

 ceedingly in shape, but are never bifoliate. The ramose habit 

 of growth pertains to a majority of the species. In the "ma- 

 ture" region the zooecia have thick walls, usually appearing 

 here as though fused together. Here too the diaphragms are 

 centrally perforated, having originally functioned as covers to 

 the zooecia apertures. Specimens preserving the opercular covers 

 are rare, and it is only in some of the Carboniferous forms that 

 the perforations are invariably shown by good thin sections of 

 the peripheral or mature region. Mesopores are usually present 

 and sometimes abundant, but they are often intermittent, and 

 generally without distinct walls and diaphragms. Acanthopores 

 well developed. Intramural dots are also shown in tangential 

 sections of most species. 



The six genera Batostomella, Stenopora Lonsdale, Aniso- 

 trypa, Bythopora Miller and Dyer, Callotrypa Hall, and Leio- 

 clema almost seem an incongruous assemblage, yet after a very 

 careful comparison, I do not see how they are to be kept separate. 

 Being intermediate in its construction, Batostomella, is selected 

 as the type of the family. From that genus we can trace easy 

 gradations into Callotrypa, through Bythopora. On the other 

 hand Batostomella nitida, from the Chester group, is not at 

 all far removed from good species of Stenopora, while again it 

 is easy to show a very decided affinity between Stenopora and 

 Anisotrypa. On account of the diverse structure of the different 

 genera comprised in the family, I have found much difficulty in 

 grasping the really significant characters of the group, and I 

 am not certain that they are all mentioned in the above brief 

 definition. Still I believe our present requirements are satis- 

 fied. 



Comparing the BATOSTOMELLID.E with other families, I find, 

 first, that the Lower Silurian species of Batostomella are related 



