NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
265 
Rent ; the opesiules are large, round, and dissimilar; the opesium is surrounded 
by a small, improminent collar (oral arch). 
a zooecia 
' Lz— 0.75-0.85 mm. 
I 0.55 mm. 
i,, . r\ ■ fA<?=0.30mm. 
Measurements . — Opesium 7 - 
(Zu=0.40mm. 
. fZs=1.25mm. 
B zooecia 7 
\lz= 0.60 mm. 
Variations. — This species is rather constant in its characters. The partition 
which separates the two chambers is horizontal in the a and B zooecia, so that both 
kinds of zooecia are provided with a polypide tube, a condition which does not 
exist in the preceding species studied ( Steganoporella jacksonica , etc.) (figs. 3, 4). 
The tube is seen complete after very gently rubbing away the surface of the 
zoarium (fig. 5). 
The dissymmetry of the opesiules is constant, but it is not very great, and cer- 
tainly the retractor muscles of 
the polypide were not attached in 
one of the proximal angles of 
the zooecium. 
In this section it appeared 
to us that the frontal was a 
tremocyst resting on an olocvst, 
but this is a point to be verified. 
The zooecial mural rim is an 
olocyst whose elements are 
grouped in radial rows around 
the opesium (fig. 6). 
The zoarium may attain a 
length of 2 centimeters ; the size 
of the zooecia permits its deter- 
mination with a simple hand 
lens. This is a goocl-sized fossil 
and can be readily employed in 
field determinations. 
Occurrence. — Vicksburgian (Marianna limestone) : West bank of Conecuh 
River, Escambia County, Alabama (common) ; Salt Mountain, 5 miles south of 
Jackson, Alabama (common) ; Murder Creek, east of Castlebury, Conecuh County, 
Alabama (common); Claiborne, Monroe County, Alabama (common). 
Cotypes . — Cat. No. 64257, U.S.N.M. 
B *7S 
D *40 
A *40 
Fig. 72. — Genus Siphonoporella Hincks, 1880. 
A-D. Siphonoporella delicatissima Busk, 1840. A. View 
of zooecia, X 40, with covering membrane removed. B. 
Zooecium of same, X 75. C. Zooecium, X 75, showing 
proximally directed part of polypide tube. D. View from 
the basal surface, X 40. (A-D after Levinsen, 1909.) 
Genus SIPHONOPORELLA Hincks, 1880. 
1880. Siphonoporella Hincks, General History of Marine Polyzoa, 1. Madeiran Polyzoa, 
Annals Magazine Natural History, ser. 5, vol. 6, p. 22. 
The proximal calcified pad of the frontal wall is formed by a larger or smaller 
arched gymnocyst; the aperture is not surrounded by a projecting margin; the 
zooecia occurring only in a single form and provided with a small, always unarmed 
