BRYOZOA. 129 
Rhinidictya ] 
Ruwinipictya PAUPERA Ulrich. 
PLATE V, FIGS. 19-21. 
Stictopora paupera (part.) ULRICH, 1886. Fourteenth Ann. Rep. Geol. Nat. Hist. Sury. Minn., p. 69. 
Zoarium usually less than 30 mm. high, consisting of narrow parallel-sided 
branches, dividing dichotomously at intervals of from 4.0 to 12 mm. Near the base 
the intervals are usually less than 6.0 mm., but further up the prevailing distance 
between bifurcations is about 8.0 or 9.0 mm. The width of the branches is fairly 
constant, deviating but little either way from 1.3mm. Their thickness has not been 
noticed to exceed 0.5 mm. Zocecia with nearly direct oblong apertures, their shapes 
varying with age from subquadrangular to elliptical. Interspaces rather narrow, 
or of moderate thickness. Zocecial apertures usually in ten or eleven rows, but eight 
or nine and twelve rows often occur just after and before bifurcations. The central 
five or six rows are arranged between raised longitudinal lines, minutely granulose 
when perfect, while the two or three rows on each side are, besides being slightly larger 
than usual, directed obliquely outward. Five of the central rows in 0.7 or 0.8 mm ; 
measuring lengthwise along same eighteen or nineteen apertures in 5.0 mm. Internal 
structure very much as in young examples of #. mutabilis Ulrich. 
In the above diagnosis I have restricted my observations to the Minnesota form 
occurring in the upper division of the Trenton shales at St. Paul and Cannon Falls. 
This form should be regarded as the type of the species, and, pending further investi- 
gations, the wisest course seems to be to restrict the use of the name to it. The 
Kentucky and Tennessee form, occurring in the shaly upper member of the Trenton 
group in those states, which I have referred to this species (loc. cit.), is now regarded 
as distinct and next described as R. neglecta. I have two specimens from the “ Phyl- 
loporina beds” at St. Paul that are exceedingly like, if not identical with the latter, 
but so far it has not been found in the shales above these beds, nor in the Galena 
limestone division of the Trenton in Minnesota. But several examples collected 
from the Galena shales at localities near Cannon Falls, seem to be identical with the 
Canadian form referred to Rk. paupera in 1886. <A very fine example, with branches 
spread over a space 50 mm. wide by 75 mm. long, collected at Ottawa and kindly 
given to me by Mr. Walter R. Billings, causes me to doubt the strict propriety of that 
reference. This specimen shows that the Canadian form agrees with typical hk. pau- 
pera in this, that the number of zocecial apertures in 5 mm., measuring lengthwise, 
is eighteen to nineteen. Continuing our comparisons, however, we find the follow- 
ing differences: (1) the apertures are smaller and rounder, and haye a more distinct 
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