298 THE PALEONTOLOGY OF MINNESOTA. 
[Batostoma? decipiens. 
BaTOSTOMA? DECIPIENS, ”. Sp. 
PLATE XXVII, FIGS. 16-19. 
Zoarium ramose, branches smooth, 5 to 12 mm. in diameter. Zocecia with 
moderately thick walls; apertures polygonal, subequal, about eleven in 3 mm. 
When in a good state of preservation the walls are sharply ridge-shaped, appearing 
thinner than usual. Clusters of large cells scarcely distinguishable. Mesopores 
very few, acanthopores not observed at the surface. 
Internal characters: Vertical sections show that in the axial region the proximal 
end of the tubes is crossed by four to six diaphragms, 0.2 mm. or less apart. Above 
these the distance between them is from two to four times as great until the tubes 
are about to turn into the well defined peripheral region, when their number is 
greatly increased. In the outer part of the tubes, where the diaphragms also 
exhibit a tendency to coalesce, the number varies in different sections from seven 
to twelve in 0.5 mm. 
In tangential sections the walls are thick, though some difference in this respect 
is noticeable in the ten sets of sections prepared. This is owing to the varying 
thickness of the internal concentrically laminated deposit. The divisional line 
between adjoining tubes is sharply marked, and sometimes contains a small, 
acanthopore-like dot midway or thereabout between the angles of junction. The 
mesopores, which are scattered very sparingly among the zocecia, and sometimes 
gathered into clusters of three or four, look very much as though they might be 
merely young or perhaps aborted zocecia, differing from them, so far as can be seen 
in these sections, solely in the matter of size. 
The systematic position of this species cannot be determined finally until we 
know more of the Chazy Trepostomata. Without that knowledge its affinities appear 
to lie as closely with B. winchelli on the one hand as with Callopora angularis on the 
other. I thought much of classing the species with Callopora, but at last concluded 
that the occasional presence of acanthopores and greater thickness of the walls 
would not now admit of such an arrangement. Callopora angularis, which of all the 
associated species is probably the most like B.? decipiens, has smaller branches and 
thinner zocecial walls. 
Formation and locality.—Rather rare in the lower and middle third of the Trenton shales at Min— 
neapolis, Minnesota. 
