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THE PALEONTOLOGY OF MINNESOTA. 
[Batostoma winchelli. 
Internal characters: Being an exceedingly common and superficially variable 
species, over thirty sets of thin sections were prepared. These prove the species 
constant in most of the characters shown in vertical sections, and decidedly variable 
in tangential sections. It should, however, be stated that many of the specimens 
sectioned exhibited some external peculiarity or deviation from the ordinary types 
of the species. In the axial region of vertical sections the tubes are thin-walled 
and crossed by diaphragms from one to three times their diameter distant from 
each other. But in the attenuate proximal ends of the tubes the diaphragms are 
always closer than after the tubes have attained their full size. In entering the 
peripheral region, the width of which depends upon age, the tubes bend outward ~ 
rather abruptly, proceeding thereafter directly to the surface. In the turn the 
diaphragms become more numerous and, though generally straight and complete, 
not infrequently exhibit a tendency to coalesce with each other. In the mesopores, 
which sometimes evidently changed into zocecial tubes, the diaphragms occur 
regularly seven in 0.5 mm. 
In figs. 4 to 8 on plate XXVII, I have endeavored to represent the principal 
variations noticed in tangential sections. The most of them are as in fig. 6, and 
figs. 4 and 5 represent what I-regard asa condition of extreme age, differing from the 
usual condition merely in having an extra internal deposit of hard tissue. Figs. 7 
and 8, however, deviate in a more important respect in having stronger and more 
abundant acanthopores. Many of these, furthermore, are developed between the 
angles, causing an inbending of the tube-walls. The average size of the zoccia 
in this form, which may receive the provisional name of var. spinulosum, is also a 
trifle greater than usual. 
The systematic position of this and the two species following is somewhat 
doubtful, but after careful reflection I have selected Batostoma as more fitting to 
receive them than Amplexopora. The closer tabulation of the proximal ends of the 
tubes, the irregularity of the tubes in the axial region, and their division there (as 
seen in the central part of transverse sections) into a large and small series, are 
characters so far unknown in Amplexopora. But my chief reason for placing the 
species with Batostoma is found in the marked resemblance exhibited by fig. 8 to 
similar views of B. implicata and B. jamesi of the Cincinnati rocks. 
Formation and locality.—Very abundant in the middle third of the Trenton shales at St. Paul, 
Minneapolis, and localities in Goodhue and Fillmore counties, Minnesota. 
Mus. Reg. Nos. 5999-6001, 8092, 8095. 
