BRYOZOA. 129 
Distribution.] 
an imaginary axis to the surface where they bend outward abruptly, often becoming 
free and much produced. Apertures circular, sometimes scattering, usually arranged 
in regular transverse or subspiral series. 
Type: M. cinctosum Ulrich, Chazy (perhaps lower Birdseye) limestone of Ken- 
tucky. 
Fuller investigations and comparisons with typical and authentic examples of 
Entalophora and Clonopora are necessary before we may be said to be in a position to 
decide peimanently the merits of this genus. Hntalophora, as now understood by 
Hincks and Waters, seems to me to be too comprehensive and might be, with advant- 
age to classification, divided into at least two groups of generic rank, and it is not 
at all improbable that Mitoclema stands upon unoccupied ground. In the mean time 
no harm can result from the use of the name for these early paleozoic species. 
Mrroctema(?) mMunpuLum Ulrich. 
PLATE II, FIGS, 4-6. 
J 
Mitoclema ? mundulum ULRIcH, 1890. Jour. Cin. Soc. Nat.Hist., vol. xii, p. 177. 
Zoarium ramose, yery small, the branches cylindrical, 0.5 or 0.6 mm. in diameter, 
with faint transverse striz or wrinkles over the spaces between the zowcial apertures. 
The latter are drawn out tube-like, about 0.15 mm. in diameter, and project strongly 
upward and outward from the surface of the small stems. Their arrangement is in 
rapidly ascending spiral series, with four or five in 2mm. As near as can be deter- 
mined from the material at hand, the zowcial tubes diverge equally to all sides of 
the branches from an imaginary axis. 
Owing to the absence of specimens suitable for slicing the internal characters of 
this species have not been determined. The generic position is therefore somewhat 
questionable, since it may prove to have the structure of Diploclema Ulrich (Geol. 
Sur. Ill., vol. viii, p. 368), founded upon D. trentonense Ulrich, a similar form occur- 
ring in the Trenton limestone of New York. In Diploclema the branches are slightly 
compressed, and the zocecial apertures somewhat constricted and less prominent.* 
Formation and locality.—Associated with the preceding in the topmost beds of the Trenton shales, at 
Cannon Falls, Minnesota. 
Mus. Reg. No. 8103. 
*In his paper on Wenlock shales Bryozoa Mr. Vine has described several similar species which he originally referred to 
Spiropora and later to Entalophora Of these S. regularis is an unquestionable Diploclema and closely allied to our Niagara 
D. sparsum Hall, sp. The others I have not had an opportunity of examining. 
