208 THE PALEONTOLOGY OF MINNESOTA. 



[Phylloporlna. 



On the other hand, in P. aspera Hall, P. reticulata Hall, P. dawsoni Ulrich, and P. 

 (tsperato-striata Hall, the zooecial tubes are shorter and thus approach the ordinary 

 cryptostomatous cell more nearly. Indeed, P. dawsoni can be, I think, shown to be 

 the first recognizable stage in the line of development that later on resulted in the 

 highly diversified Fenestellidce. This same species, however, and the remark applies 

 with equal force to Drymotrypa dichotoma Ulrich, has much to remind us of Cyclosto- 

 mata like Protocrisina, the zooecial orifice being but little constricted and the enclos- 

 ing rim similarly prominent in all of them. 



We can show, therefore, apparent relations to three suborders of Bryozoa, and it 

 becomes a question of some difficulty to decide where the family had best be placed. 

 The Cryptostomata, however, seem best adapted to receive them, chiefly for the rea- 

 son that the Phylloporinidce and Fenestellidm are doubtlessly derived from the same 

 stock, and the latter developed from the branch of the former mentioned. 



* 



Genus PHYLLOPORINA, Ulrit-h. 



Betepora, as applied by various authors to Lower and Upper Silurian anastomosing Bryozoa (not 



Lamarck, 1801). 



Gorgonia ?, HALL, 1847, (not Gorgonia Liniucus, 1745). 

 Intricaria, HALL, 1847 ; MILLER and DYJSU, 1878, (not Defrance, 1823). 

 Pltyllopora (part.), ULIUCH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 150. 

 Nov. gen. (uudesc.), ULIUCH, 1886. Contri. to Arner. Pal., vol. i, No. 1, p. 5. 

 Phylloporina, Unticn, 1890. Geol. Surv. 111., vol. viii, pp. 399 and 639. 



Zoaria retiform, consisting of somewhat irregularly anastomosing, slender 

 branches, with from two to eight ranges of zocccia on the obverse side. Reverse 

 convex, longitudinally striated, without apertures. Zocecia tubular, often with the 

 immature region very long, commonly with diaphragms. Apertures simple, uncon- 

 stricted, rounded or subangular, generally with a peristome. Mesopores present, 

 sometimes numerous, always closed at the surface ; with diaphragms. Acan- 

 thopores often present. 



Type : P. trentonensis (Retepora trentonensis Nicholson,* compare Retepora fene- 

 strata~Ka\\-\). 



This genus includes some of the earliest types of Bryozoa known. Beginning in 

 the Chazy with three closely related species, the genus continues in the Birdseye 

 and Trenton with six or seven well-marked forms, four of which are described in the 

 following pages. In the Cincinnati group we have two species, in the Clinton one, 

 and in the Niagara one. The genus is not known from later deposits. 



The affinities and natural relations of the genus have already been touched 

 upon in discussing the family. There remains to compare with Retepora, Imperato, 



Geological Mag., vol. 2. p. if!, 1875. 



+Third Report N. Y. St. Mus. Nat. Hist., p. 178. 1850. 



