PROUT — NEW SPECIES OF BRYOZOA. 413 



Longitudinal rays more or less irregular in size, full, 

 round, and appearing under the microscope as minutely cel- 

 lular, in a thickened, strong basis. 



Dissepiments nearly as large as longitudinal rays, and 

 not depressed, being on a level with the raj^s. 



Fenestrules or oscules slightly oval, giving the appearance 

 of a perforated plate rather than of regular partitions by 

 raj's and dissepiments, arranged in beautiful waved lines. 



Medallion face. — Longitudinal rays with about three lines 

 of minute pores, and about three to each oscule, much 

 crowded, so as to nearly fill the open spaces of the oscules, 

 and, as far as can be seen, with chalices upon the dissepi- 

 ments; oscules oblong oval; 5 long, and 6 trans, in a spaco 

 of 2 lines. ^ ^ 



Hamilton Group. — \_Illinois State Collection.'] 



Ptilodictya (Stictopora) variabilis, Prout. JC J i— * * 



Bryozoum branched once, celluliferous on both sides ; ;.'<;' 



kl In Arm I /~\ 1 1 4- i-\ ■*» HAirr net I r» -»» i-<» j-* nn 4 Wa^a i tr\ 4- V* n *v»^ /-I J 1 a l«»J. " m 



cells oval, outer row as large as those in the middle, but n ~fr*~ 

 bryozoum. The body and branches marked by from six tort/***^ \ 



terminating sooner on the round and smooth margin of the 



ten lines of oval cells, which, when perfect, have somewhat 

 elevated round borders. Cells originate from the opposite 

 sides of a central lammella or plate, which is probably 

 double from the partial cementation of the cells at their 

 bases. Celluliferous portion moderately thick, though flat- 

 tened. 



This species is certainly very^. closely allied to, if not • 



identical with, P. acuta, Hall. It has the same form and 

 arrangement of the cells, with the exception of the cells 

 being as large on the outside as on the middle rows. It 

 differs, moreover, in the edges of the branches not being 

 acute but rounded, but above all by the existence of a cen- 

 tral lammella or plate which separates the opposite and less 

 flattened portions of the bryozoum. 



Geol. Pos. & Loc. — Upper Silurian, Columbus, Ohio. — 

 ^Illinois State Collection^ 



