BRYOZOA. 139 
Eurydietya all 
EKurypicrya MuLTIPORA ? Hall, sp. 
PLATE VI, FIGS. 9-11; PLATE VII, FIGS. 24 and 29-31; PLATE XIV, FIGS. 9-11. 
? Phenopora multipora HALL, 1851. Geo. Lake Sup. Land Dist., vol. ii, p. 206. 
Phenopora (?) multipora ULRICH, 1882. Jour. Cin. Soc. Nat. Hist., vol. v, p. 171. 
Eurydictya multipora ULRicu, 1890. Geol. Surv. IL, vol. viii, p.520. (Referred to new genus only.) 
. 
Zoarium forming irregularly divided wide fronds, 6 to 20 mm. in width, or simple 
undulating expansions, or a combination of the two. The Minnesota example figured 
on plate XIV is a fragment of a slightly undulating expansion, 0.7 mm. to 1.5 mm. 
thick, that must have been no less than 20 mm. wide. The others are of less width, 
and one (plate VII, fig. 24) deviates so widely from the ordinary growth that it was 
at first believed to belong to Rhinidictya mutabilis var. major. 
Surface with irregularly distributed small maculz, often very inconspicuous and 
scarcely interrupting the regularity of the longitudinal ridges. In other cases they 
may appear as smooth solid spots, fully 1 mm. in diameter. As a rule they give one - 
the impression of a variable number of elongate zocecia filled with a solid deposit of 
calcareous material. Zocecial apertures subelliptical, more or less oblique, (generally 
more so than in fig. 11, plate XIV) with a slight peristone, strongest at the posterior 
margin, arranged between rather prominent, granulose, longitudinal ridges, seven- 
teen or eighteen in 5 mm.; also in curved diagonal series, but these are never very 
regular and frequently turn into transverse rows. Measuring transversely, from 
twenty-three to twenty-six of the longitudinal rows may be counted in 5 mm. The 
width of the interspaces is usually about equal to the diameter of the apertures. 
When the latter are partially filled with the clayey maxtrix, they may appear as of 
subquadrate shape, with the interspaces thinner than usual. In the narrow or basal 
part of the fronds, the spreading edges are sharp, non-poriferous, and_ striato- 
granulose, while several of the marginal rows of the zocwcial apertures may be 
directed obliquely outward. 
Vertical sections show that the primitive cell is rather high, short, and has thin 
walls. ‘These curve over it to a point marking the beginning of the vestibular por- 
tion of the tube, when they bend sharply outward. At the same time the interspaces 
(walls) are greatly widened, and three to five shallow vesicles are developed in direct 
sequence. Above these the interspaces are solid and seemingly structureless, if we 
except a dark line running lengthwise through them. No diaphragms observed. 
Tangential sections may present one or all of three distinct phases or stages in 
the development of the zoarium. Their exhibition depends upon the distance from 
the median lamine at which the zocecia are cut by the section. In the first or deep- 
est part of the section, the zocecia are quadrate, thin-walled, and arranged in regular 
