BRYOZOA. 307 
Monotrypa (? Chetetes) cumulata.] 
In the absence of any knowledge of the interior the generic position of the 
species is necessarily a little doubtful. In a general way, M. nodosa resembles 
Leptrotypa filiosa d’Orb. sp., of a lower horizon in the Hudson river rocks, very closely, 
and the principal difference that can now be pointed out is in the size of the zocecia, 
that species having eleven or twelve apertures where the present form has nine or 
ten. But Atactoporella ortoni Nich. sp., to which Whitfield referred the Wisconsin 
specimens, is a delicate parasitic form totally distinct. 
Formation and localityx—Common in the upper beds of the Hudson river group at Iron Ridge and 
Delafield, Wisconsin, and Savannah, Illinois. 
Mus, Reg. No. 7574. 
Monorrypa (? CH&TETES) CUMULATA, 2. Sp. 
PLATE XXVII, FIGS. 26 and 27, 
Zoarium forming small subglobular or irregular masses, generally consisting 
distinctly of irregularly superposed layers ; average sizes between 15 and 20 mm. in 
diameter, anything under or over those extremes being rare; no monticules. 
Zocecial walls thin; apertures polygonal, of unequal sizes, sometimes forming at 
long but irregular intervals large clusters in which they are conspicuously larger 
than elsewhere ; in most cases however the apertures are subequal, with an average 
of six and one-half or seven in 3 mm. Mesopores and acanthopores wanting. 
Internal characters: In vertical sections the tubes diverge rapidly and rather 
irregularly, and their walls present an obscure longitudinal lineation. Diaphragms 
occur at intervals varying from one to four times their diameter, but their position 
in neighboring tubes corresponds approximately. In transverse sections the prin- 
cipal interest attaches to the structure of the walls. In most sections the wall 
is comparatively thick and seems to be composed of minute columns which, being 
cut transversely, appear as alternately dark and lighter parts. In this respect the 
structure of the walls is essentially the same as in true Chetetes, and I would un- 
hesitatingly have placed the species into that genus had I been able to satisfy 
myself that the phenomena observed were not-the result of secondary causes. 
Namely, in some sections the appearance is very different, the wall itself being more 
sharply defined and thinner than usual (especially where the tubes are filled with 
matrix instead of calcite) and without the alternating light and dark spots. But 
where the tubes are filled with calcite the latter for some distance inward from the 
wall is of a darker color than at the center, and exhibits, strange to say, a spotting 
not unlike that pertaining to the wall itself in other sections. 
