206 ~ THE PALEONTOLOGY OF MINNESOTA. 
[Nematopora. 
ora like R. lineinodis Ulrich, and R. regularis (Trematopora and later Orthopora regu- 
laris Hall), but it is to be doubted that this resemblance is indicative of even remote 
relation. In Rhombopora the primitive cells are drawn out into long tubes which 
originate, just as they do in nearly all of the ramose T'repostomata, in various parts of 
the axial region. In Nematopora, on the other hand, the zowcia are comparatively 
short and arise along a definite axial line. 
Formation and locality —Galena shales, near Cannon Falls, Minnesota. 
Mus. Reg. No. 8111. 
NeEMATOPORA DELICATULA Ulyich. 
PLATE III, FIGS. 26 and 27. 
Nematopora delicatula ULricn, 1890. Geol. Sur. I1l., vol. viii, p. 646. 
Zoarium very small and exceedingly slender, ramose above the pointed basal 
extremity. Branches quadrangular, with the angles rather sharp, and the solid 
sides flat or gently convex, each from 0.15 to 0.18 mm. wide. Zocecia rather long, in 
four ranges ; apertures ovate or subcircular, about 0.12 mm. in length, separated by 
long, smooth intervals, each from 0.7 to 1.0 mm. in length ; average length of zocecia 
about 0.95 mm. Peristome thin, easily broken away; when perfect it forms a 
sharply elevated rim about each aperture. 
The widely separated zocecial apertures, and the exceeding delicacy and quad- 
rangular form of the zoarium of this species distinguish it from all other species of 
the genus known. The associated N. ovalis often has only four ranges of zocecia, but 
their apertures are so much larger that the two species cannot be confounded. The 
possibility of confusion with N. granosa and N. conferta is equally remote. Indeed, 
all of these four associated species are distinguished by sharply marked and easily 
recognized peculiarities. 
Formation and locality.—Galena shales, near Cannon Falls, Minnesota. The original types of the 
species were collected from an equivalent horizon in Alexander county, Illinois.* 
Nemaropora conrerta Ulrich. 
PLATE ITI, FIGS. 21-23. 
Nematopora conferta Utnicn, 1890. Jour. Cin. Soc. Nat. Hist., vol. xii, p. 198. 
Zoarium ramose, spreading nearly in a plane; branches dividing dichotomously 
at intervals varying from 1 to 3 mm., 0.4 to 0.5 mm. in diameter, subcircular in cross- 
section. Zocecia in five or six longitudinal ranges, their apertures frequently arranged 
*In the Ill. Geol. Surv. vol. vill, this horizon is given, in conformity with the preceding volumes of publications of 
that survey, as Cincinnati group, but at the top of p. 645 (op. eit.) it will be seen that I express a doubt as to their exact 
age, saying that “I am inclined to regard them as more likely representing an upper member of the Trenton group.” I 
have now satisfied myself that they are equivalent to the Galena of the Northwest and the Trenton Mmestone of New York. 
