332 THE PALEONTOLOGY OF MINNESOTA. 
(Ceramophylla frondosa. 
are 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. j 
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 Hurydictya multipora 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.x—Over 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. Reg. No. 8381. 
Nore:—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 with 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. 
