BRYOZOA. 207 



PhylloporinidaB.] 



also in rows encircling the stems. Apertures rounded or broad-oval, slightly oblique, 

 about 0.15 'mm. in diameter, separated lengthwise by intervals a little greater than 

 their diameters, with seven or eight in 2.5 mm.; peristomes thin, strongest and 

 most elevated posteriorly. Interspaces striated, occasionally rising into strong ridges 

 which separated the longitudinal ranges of zooecial apertures for a short distance. 



The smaller, subcircular apertures and differently marked interspaces, distin- 

 guish this species from N. ovalis. In N. granosa the zooecial apertures are much nar- 

 rower and alternately arranged, while the interspaces are papillose. N. alternata 

 Ulrich, from a similar horizon in southern Illinois, has the zooecial apertures 

 arranged in quincunx, and differs in other obvious particulars. 



Because of the rounded zooecial apertures and their prevailing mode of arrange- 

 ment, the branches of this species sometimes resemble those of Protocrisina exigua 

 Ulrich, a cyclostomatous'form that is associated with it at Cannon Falls. This 

 resemblance may prove a little troublesome when the surface of the Nematopora is 

 slightly abraded so that the striation of the interspaces is obscured. In all cases, 

 however, when the specimens can be observed free from the matrix they may be 

 distinguished at once by the fact that in the Nematopora the surface is celluliferous 

 on all sides, while in the Protocrisina one side of the branches is striated longitu- 

 dinally and without zooecial apertures. 



Formation and localitif-— Galena, shales, near Cannon Falls, Minnesota, where it is associated with 

 the preceding species and many other small Bryozoa. Prasopora insularis Ulrich, is the commonest and 

 most characteristic fossil of this horizon. 



Family PHYLLOPORINID^, Ulrich. 



The genera comprised in this family, Phylloporina, Drymotrypa and Chainodidyon, 

 are not very important in the way of specific and individual representation, but viewed 

 from a biologic standpoint they are decidedly interesting. This interest attaches 

 chiefly to the fact that they furnish excellent examples of what have been very aptly 

 termed " comprehensive types." 



A careful investigation of the internal structure of the various species of Phyllo- 

 porina leads us to the conviction that at some time prior to the age of the Chazy 

 there existed Bryozoa that combined characters which, during subsequent periods, 

 became separately specialized and characteristic of widely different groups of fami- 

 lies. Take for instance, P. trentonensis Nicholson, sp., or P. sublaxa, P. halli and P. 

 corticosa of the present work. In all of these remarkable forms we are reminded 

 very strongly of typical Trepostomata, the subangular zooecial tubes, their long ''im- 

 mature" region, diaphragms, mesopores and acanthopores being, all of them, char- 

 acteristic of species of that suborder. 



