NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
201 
Occurrence. — Jacksonian (Zeuglodon zone) : Cocoa post office, Choctaw County, 
Alabama (rare). 
Geological distribution. — Rupelian ( = Stampian) of Germany. 
Plesiotypes. — Cat. No. 63957, U.S.N.M. 
Division II. COILOSTEGA Levinsen, 1909. 
The parietal muscles are attached to the ectocyst and traverse the ehitinous or 
partially calcified cryptoc.yst by means of the opesiules. The hydrostatic system is 
zoarial but each zooecium in addition is provided with a hypostege with the cryp- 
tocyst calcified. 
The families of this division are as follows, all except the last three being 
represented in the present work : 
ect 
Opesiulidae Jullien, 1888. 
Subfamily Microporidae Hincks, 1880. 
Onychocellidae Jullien, 1881. 
Lunulariidae Levinsen, 1909. 
Aspidostomidae Canu, 1908. 
Steganoporellidae Levinsen, 1909. 
Thalamoporellidae Levinsen, 1909. 
Setosellidae Levinsen, 1909. 
Chlidoniidae Levinsen, 1909. 
Alysidiidae Levinsen, 1909. 
Family OPESIULIDAE Jullien, 1888. 
Fig. 54. — Structure of the Coilo- 
stega. 
Diagrammatic transversal section 
of a zooecium of the Coilostega. 
(After Harmer, 1902.) crypt , calci- 
fied cryptocyst; ect, membranous 
ectocyst; ople, opesiule containing 
a depressor muscle ( depr ), or modi- 
fied parietal muscle. 
The parietal muscles are attached to the crypto- 
cyst; their place is indicated either by pores or by lateral indentations called 
opesiules. The ovicell is endozooecial. 
Historical. — In 1886 Jullien discovered that the parietal muscles in many 
genera of bryozoa were attached to the cryptocyst ; these he grouped in the division 
Opesiulae (Coilostega Levinsen). His incomplete studies led him to conceive but 
a single family, the Opesiulidae. Successively other authors have erected the fol- 
lowing families : 
Steganoporellidae Levinsen, 1909. Setosellidae Levinsen, 1909. 
Aspidostomidae Canu, 1908. Microporidae Hincks, 1880. 
Thalamoporellidae Levinsen, 1909. 
In 1909 Levinsen discovered that in Onychocella the parietal muscles are also 
attached to the ectocyst, and as the ovicell here is also endozooecial, it became 
necessary to group the Onychocellidae with the Microporidae. Previous to this, 
Jullien had remarked that his genus Woodipora of the Opesiulidae had some in- 
credible resemblances to the Onychocellidae. Finally, having observed the endo- 
zooecial ovicell in the Lunulariidae, we are obliged to group in the same family of 
the Opesiulidae, the three ancient families of the Microporidae, Onychocellidae, and 
