American Paleozoic Bryozoa. 267 
of just as much importance: namely, the interstitial tubes of 
‘Stellipora antheloidea originate, the same as the true zoccia, from 
the epithecal membrane, while in C. florida, and other species of Con- 
stellaria, they are developed from the true zocecia as these bend from 
the axial, and enter the peripheral region.’ Furthermore, while the 
“immature” portion of the zoccial tubes in Constellaria is very long, 
it is exceptionally short in Stellipora. 
CONSTELLARIA FLORIDA, Ulrich (Pl. XIV., figs. 2-2/7). 
When I described the external characters of this species in an 
earlier portion of this work, I excused myself from giving the complex 
internal characters, as I was unable then to illustrate them. I promised 
to complete the description when the genus, in its turn, should come 
up for consideration. I now fulfill that promise. 
Tangential sections (Pl. XIV.., figs. 2c, 2d, and 2e), when they cut 
the zoarium just below the surface, present two distinct phases, which, 
in sections exhibiting the two extremes, are connected by gradual in- 
termediate stages. The appearance usually obtained in sections of 
this kind, is represented by fig. 2c. This shows that the maculae, 
which at the surface appear to be subsolid, are in reality composed of 
numerous very thin-walled, often elongated, ‘angular interstitial cells, 
varying greatly in size from the central portion of the maculum, where 
they are larger than the true zocecia, to the extremities of the rays, 
. where they usually are not more than half as large. Between these 
rays, from five to fifteen of the true cells are aggregated into irregularly 
elliptical, compact groups. The form of these cells is sub-elliptical, 
on account of being so compactly wedged together. In the inter-mon- 
ticular spaces the true zocecia are distinguished by their circular form, 
and thicker walls ; they are sometimes completely isolated by a single 
series of rather large interstitial cells, though it is more common to see 
them partially in contact. When the section is cut from a sufficiently 
matured example, the phase represented by fig. 2d, may be observed. 
In this the walls of the true zocecia.are comparatively thick, and (the 
most noticeable feature) the interstitial cells in the macule, can 
scarcely be recognized. All the spaces known to be occupied by inter- 
stitial cells, now appear to be sub-solid and occupied by a mass of 
sclerenchyma, within the substance of which, numerous small, dark 
spots are noticed, generally enclosing a smaller lucid one. i am satis- 
fied that these represent minute foramina, which perforated the succes- 
sive interstitial membranes, and that they are precisely of the same 
