174 THE PALEONTOLOGY OF MINNESOTA. 



[Phamopora. 



specimens of the European species, described mainly as Ptilodiclya, that I suspect 

 to belong to this genus. Under the circumstances it would not be safe to include 

 them. 



Section a, zoaria simple, without monticules. 



Plicenopora ensiformis Hall, Clinton group, New York, Canada, Ohio and Indiana. 

 P. lonsdalei (Ptilodictya lonsdalei Vine), Wenlock shales, England. 

 P. tenuis Hall, Lower Helderberg group, New York. 



Section b, zoaria simple, with monticules. 



Phcenopora bipunctata (Ptilodictya bipunctata (Van Cleve) Hall,) Clinton group, Ohio. 



P. constellata Hall, Clinton group, New York and Canada. 



P. expansa Hall and Whitfleld, Clinton group, Ohio. 



P. punctata (Ptilodictya punctata Nicholson and Hinde), Clinton group, Canada. 



P. svperba (Ptilodictya superba Billings), Anticosti group, Anticosti. 



P. wilmingtonensis Ulrich, Cincinnati group, Illinois. 



Section c. zoaria branching. 



Phcenopora excellens (Ptilodictya excellens Billings), Anticosti group, Anticosti. 



P. explanata Hall, Clinton group, New York and Canada. 



P. fimbriata (Ptilodictya fimbriata James), Clinton group, Ohio. 



P. incipient Ulrich, Trenton group, Canada and Vermont. 



P. lindstroemi Ulrich, Upper Silurian, Gotland. 



P. magna (Stictopora magna Hall and Whitfleld), Clinton group, Ohio. 



P. multifida (Stictopora multifidn (Van Cleve) Hall), Clinton group, Ohio. 



Though fully convinced that some of these species are synonymous, it seemed 

 best to retain all names until an opportunity offers to treat the genus in a mono- 

 graphical way. 



PH.ENOPORA INCIPIENS n. sp. 



PLATE XIII, FIGS. 14-17. 



Zoarium small, dividing dichotomously at rather long intervals ; basal extremity 

 long, slender, subcylindrical, with fewer and more elongate zooecial apertures than 

 above the first bifurcation. Branches 1.5 to 2.0 mm. wide, compressed, rigid, edges 

 sharp, parallel, with moderately developed striato-punctate, non-poriferous border. 

 Zooacia in from twelve to fifteen alternating ranges, very regularly arranged in long- 

 itudinal, diagonally intersecting and transverse rows, with respectively eleven in 

 5 mm., ten in 2.5 mm., and five in 1 mm. Zooecial apertures of equal size, elliptical, 

 enclosed in a minutely papillose rim or peristome, the latter slightly depressed at 

 the ends, and generally in contact with each other at four points, so that with a side- 

 light the apertures may appear as arranged between alternately converging and 

 diverging raised lines. End interspaces elongate, depressed, commonly occupied by 

 two mesopores, in other cases by three, and rarely, except in the marginal rows, 

 by four or more now in double rows ; always disposed in a longitudinal manner. 

 Non-poiiferous border occupied by two or more rows of mesopores. 



