BRYOZOA. 143 
Phyllodictya.] 
drawn out anteriorly, with the posterior edge abrupt and slightly elevated, arranged 
in straight or curved, diagonally intersecting lines, and, less obviously, in longitudinal 
series, with about seventeen in the former and twelve in the latter in 5 mm. _ Inter- 
spaces separating the apertures in the diagonal rows narrower than the apertures, 
while those between their ends may be wider and concave instead of rounded, with 
the posterior rim extending up along their sides. When in a good state of preserva- 
tion a row of minute papilla crowns this rim, and thus extends around the posterior 
margin of the zoccial apertures and up their sides to the row belonging to the suc- 
ceeding aperture. There are therefore two rows of these papillae between neighbor- 
ing apertures, but it is not uncommon to find the spaces between the apertures in 
the diagonal rows too narrow for their full development, and then they are crowded 
into an irregular single row. 
In vertical sections the zocecial tubes begin with a rather long prostrate cell 
from which they proceed to the surface by a gentle outward curve ; the continuance 
of this curve causes the apertural portion of the tube in old examples to be much 
more nearly direct to the surface than in their younger stages. In an average 
example a line drawn from the aperture to the proximal extremity of a tube forms 
an angle of about 35 degrees with the central laminw. Complete diaphragms to the 
number of five have been observed to cross each tube. Near the central axis the 
walls are thin, but soon they begin to spread, admitting of the intercalation of from 
three to five successive vesicles. Above these the interspaces are filled with solid 
matter, seemingly structureless except for the minute dark tubuli traversing them 
in a direction at right angles to the plane of the zoarium. These tubuli arise in a 
dark line running along the posterior side of the tube. 
Tangential sections show a considerable deposit of solid material on the inner 
side of the tubes. This is scarcely to be described as ring-like, since it is not sharply 
defined nor of equal thickness all around, being widest and rather indistinct anteri- 
orly, and but illy distinguished at any point from the interspaces. The latter are 
occupied by minute dark spots (median tubuli) in single or double rows, representing 
and corresponding with the arrangement of the minute superficial papille described. 
The above description is based almost entirely upon the specimen mentioned as 
having been received from Prof. C. W. Hall. Its characters, as has been stated, agree 
very closely with one type of P. frondosa, but not nearly as well with the other, pos- | 
sibly distinct form, originally united with it. Compared with P. varia, to which | 
shall provisionally refer nearly all of the Minnesota specimens of Phyllodictya so far 
seen, it will be found to differ in having thinner interspaces, and larger apertures, 
with the diagonal instead of the longitudinal arrangement predominating. Further 
