BRYOZOA. 219 
Montticulipora incompta.] 
MoNTICULIPORA INCOMPTA, ”. Sp. 
PLATE XV, FIGS, 9-12. 
Zoarium parasitic, forming inconsiderable crusts or small masses upon shells, 1 or 
2 cm. in diameter and several mm. thick. Surface even, with inconspicuous clusters 
of cells of slightly larger size than the average. Zocecia polygonal, with thin walls 
(comparatively thick for the genus), the ordinary size varying between 0.2 and 0.25 
mm, in diameter, while those in the clusters mentioned do not exceed 0.52 mm.; 
about eight in 2 mm. True mesopores wanting, the small cells being shown by thin 
sections to be merely young zoccia. Acanthopores small, inconspicuous externally. 
The internal structure is so well illustrated on plate XV that a detailed descrip- 
tion is rendered superfluous. The chief peculiarity of the species is the minutely 
cellulose and roughish character of the zocecial walls. In all other respects the 
species agrees closely enough with M. wetherbyi and M. lamellosa Ulrich, the latter 
from the Hudson River rocks of Illinois. 
Formation and locality.—Rather rare in the middle third of the Trenton shales, at Minneapolis, 
Minnesota. 
Mus. Reg. No. 5968. 
Monticutreora Granpis Ulrich. 
PLATE XV, FIGS. 1-6. 
Monticulipora grandis ULRICH, 1886. Fourteenth Ann. Rep. Geol. and Nat. Hist. Sury. Minn., p.78. 
Zoarium irregularly massive, often tending to become lobate or subramose* 
Zocecia polygonal, with thin walls. Surface without monticules, but exhibiting at 
intervals of about 5 mm. conspicuous groups of cells larger than the average ; of the 
latter nine or ten occur in 3 mm, while some of those in the clusters have been 
observed to reach a diameter of 0.5 mm. No mesopores. Acanthopores very small, 
few, practically wanting. “When perfectly preserved (see plate XV, fig. 4) the cysti- 
phragms are often to be seen in the mouths of the zocecia, giving them the false 
appearance of being very small and situated at the bottom of a wide sloping area. 
Internal structure: In the vertical sections the zocecial tubes proceed to the sur- 
face in straight or curved lines, according to the form of the zoarium. They are 
provided with thin walls and usually two more or less closely arranged series of 
_ cystiphragms, one on each side of the tube, the narrow intervening space being 
crossed by an approximately equal number of straight diaphragms. The variation 
and relative disposition of parts is shown in fig. 6 of the plate cited. The lower half 
