332 THE PALEONTOLOGY OP MINNESOTA. ^ * 



LCeramophylla Irondosa. 



aie ovate or pyriform and narrowest and highest behind, while in front of the 

 depressed anterior side of each there is either one large triangular mesopore or 

 three small ones, the whole in each case being contained in an obliquely concave 

 rhomboidal space. 



Of internal characters it is sufficient to say that diaphragms are wanting, the 

 primitive or prostrate part of the tubes thin-walled and in most cases longer than 

 the erect portion. In the latter the interspaces are very thick and, in vertical sec- 

 tions, crossed obliquely by dark lines. 



Of associated bifoliate Bryozoa only Eurydidya muUipora grows into broad 

 fronds. But the merest tyro in the science must find the task of identifying the 

 Ceramophylla an easy one. 



Formation and locality.— Oyer one hundred examples were collected at St. Paul in the upper third 

 (Phylloporina beds) of the Trenton shales. It is rarely met with in the same beds in Goodhue county. 



Mus. Beg. No. 8381. 



Note:— In the preceding report on the Bryozoa the author has adopted a merely provisional 

 nomenclature of the divisons or beds into which the Trenton formation of Minnesota is divisible, partly 

 upon lithological, but more especially upon paleontological grounds. This is in accordance v?ith an 

 agreement among the several authors at work on the paleontology of the Lower Silurian rocks of 

 Minnesota. We believed, namely, that it was best to defer the adoption of permanent names for the 

 faunal zones till the study of all the classes had been completed. The subject, therefore, will be found 

 treated in a comprehensive manner in the introductory chapter to the volume. In that chapter a full 

 list of the Trenton and Hudson River fossils found in the state is given, and each is referred to its 

 proper horizon in the series. 



