: BRYOZOA. 127 
Rhinidictya.] 
priniitive portion of the zowcia as sharply defined, thin-walled, oblong-quadrate 
spaces, the end walls of which, while approximately at right angles with the long- 
itudinal lines at the center of the zoarium, gradually assume an oblique upward direc- 
tion toward the sides. (Compare plate VI, fig. 13.) The next condition is when the 
anterior wall or side of the zocecium becomes convex, while the posterior side begins 
to extend over the cell till at last the oval aperture is formed. Now the anterior 
and posterior walls are no longer recognizable in the section, but the division between 
the longitudinal walls is clearly marked by a dark line, that, when the preservation 
of the specimen is sufficiently favorable, will be noticed to consist of a connected 
series of minute tubuli. Besides these, an occasional dark spot or tubulum may be 
noticed in the end spaces. Most of the stages so far described are shown in fig. 13, 
on plate VI, and all further phases are to be classed as old conditions. They consist 
principally of an increase in the number of minute interstitial tubuli. (See plate 
VI, figs. 1 and 4.) 
The above description does not include two forms that deserve recognition as 
varieties. Their peculiarities are not sufficiently constant to entitle them to the 
rank of species. In my preliminary report on the Minnesota Bryozoa (loc. cit.) 
another form of the species was separated as var. minor. The better and much 
more complete material since studied proves, however, that the specimens so desig- 
nated are merely young examples and therefore not deserving of a distinct name. 
Var. Magor Ulrich. 
The zoarium in this variety is more robust, the branches being wider, in some 
cases attaining a width of over 8 mm.; usually the thickness is also greater, but thin 
examples are not uncommon. Perhaps the chief peculiarity of the variety is found 
in certain grano-striate or smooth spots, which occur at rather irregular intervals 
along the center of the branches. The internal structure agrees in all essential 
respects with that of the typical form of the species, the only feature not seen in the 
latter being the solid macule. 
Mus. Reg. No. 5940. 
Var. SENILIS, 7. var. 
PLATE VI, FIGS. 2 and 3; PLAT® VII, FIGS. 16 and 1%. 
In this rather rare form the general appearance of the zoarium is like that. of 
well developed examples of the typical variety. On comparison, however, it is found 
that the non-celluliferous margin is unusually wide and sharply defined. Connected 
with this are certain narrow, irregular or subelliptical, depressed spaces just within 
the axes of bifurcation. A more important peculiarity is presented by the zocecial 
apertures. These, generally, instead of being placed in longitudinal furrows](as 
