98 THE PALEONTOLOGY OF MINNESOTA. 
(Introduction. 
TERMINOLOGY. 
Zoarium (—polyzoarium and cenecium auctt.):—The composite structure formed 
by repeated gemmation. 
Zomwcrum (—cell auctt.):—The true cell or chamber in which the polypide is 
lodged. 
Mesoporss (interstitial cells auctt.):—The angular or irregular cells which 
occupy the spaces between the zocecia in many of the T’repostomata and some of the 
Cryptostomata, 
VestouLar TissuzE:—The vesicles which occupy the space between the zoccia 
in Pachydictya, the Fistuliporide and other paleozoic Bryozoa. 
ACANTHOPORES (=<spiniform corallites Nicholson, spiniform tubuli Ulrich, Wand- 
rohrchen Dybowski) :—The tubular spines which are found in so many paleozoic 
Bryozoa, notably Dekayia, Leioclema and Batostoma. 
Mepran Tusuti ( Wandstriinge Dybowski):—Very slender tubes which are present 
between the zoecial walls and the median lamin of certain double leaved forms 
(e. g. Rhinidictyonide). Their apertures at the surface are slightly elevated and 
present the appearance of series of minute granules. The small granules in Rhomb- 
opora, Stenopora and other genera, are supposed to be of the same character. 
ComMUNICATION Pores :—Small peres which pass through the walls of the zocecia 
and establish communication between adjacent cells. 
Ocecrum (—evicell, gonocyst, gonecium auctt.):—A modified zocecium set apart for 
reproductive functions, the inflation of the zoarium in which the embryos are devel- 
oped, or a special receptacle (marsupium) which is attached to the zocecium, and 
serves the same purpose. 
DrarHracms (—tabule and septa auctt.):—The straight plates which cross the 
tubular zocecia and mesopores in the Trepostomata and a few forms of the Crypto- 
stomata. 
CystipHRAGms :——The convex plates which line the walls of the zocecial tubes in 
some of the T’repostomata (Prasopora). 
ZOCIAL COVERS (opercula) and PERFORATED DIAPHRAGMS:—Horizontal plates per- 
forated subcentrally, covering the zocecia in the Trepostomata. As growth proceeds 
in the colony these are left behind in the tubes, and mark the successive stages. 
Hemiserra :—The superior hemiseptum is a plate or laminar projection within 
the posterior border of the primitive zoccial aperture, common in the typical Cryp- 
tostomata. The inferior hemiseptum is a similar projection on the anterior wall, or 
on the median lamine of bifoliate forms, situated a short distance beneath the supe- 
rior hemiseptum. One or the other, or both may be absent. 
