BRYOZOA. 467 



series around the elevated clusters, and in diagonally intersect- 

 ing lines on the spaces between them; here six or seven occur 

 in two mm. The long diameter of the apertures varies from 

 0.25 to 0.5 mm. in the clusters. A small number of irregular 

 mesopores, about one-fourth as large as the zooecia, are inter- 

 spersed among them. 



At this time it seems highly improbable that this species is 

 congeneric with Ceramopora imbricata Hall. It is more nearly 

 related to Ceramoporella and Crepipora. and provisionally, I 

 propose to arrange the form as above. It is readily distin- 

 guished from typical species of the genus by its rather thick 

 walls and few mesopores. 



Position and locality: Cincinnati group. Common at Cincin- 

 nati, Ohio. 



DIAMESOPORA Hall, 1887. 



Diamesopora Hall. Pal. N. Y. Vol. II, p. 158. 1852. (Not defined.) 

 Cwloclema Ulrich. Jour. Cin. She. Nat. Hist. Vol. V, 1882. (Not defined.) 

 Diamesopora Hall. Pal. N. Y. Vol. VI, p. XV, 1887. 

 (For generic diagnosis see page 380.) 



This name stands for a convenient and easily recognized 

 genus of the CERAMOPORIDJE. Though already used in 1852, the 

 genus was not defined by Hall until 3887. There are no very 

 marked internal peculiarities, but the ramose form and the 

 hollow branches serve excellently to separate its species from 

 other Ceramoporoids. In these features they resemble Chilo- 

 trypn Ulr., but thin sections will immediately distinguish them, 

 as that genus is an unqualified member of the FISTULIPORID^E, 

 having vesicular tissue instead of untabulated mesopores. 



The genus is represented by one undescribed species in the 

 Trenton limestone of Canada and New York, by D. vaupeli and 

 communis Ulrich, and D. oweni, (Fistulipora oweni James,) in 

 the Cincinnati group, by D. oscula, iufi-equens, sub-imbricata 

 dichotoma, tubulosa and varia of Hall* in the Niagara group, 



* With the exception of D. dichotoma, all these species are described by Prof. Hall 

 as Trematopora. A closer examination of these Niagara forms will, I fear, prove that 

 they are not all distinguished by good specific characters. 



