NORTH AMEFJC'AX EARLY TKRTIARY BRYOZOA. 201 



Occurrence. Jacksonian (Zeuglodon zone) : Cocoa post office, Choctaw County, 

 Alabama (rare). 



Geological distribution. Rupclian ( = Stampian) of Germany. 

 PI, siotypt s. Cat. Xo. 63957, U.S.N.M. 



Division II. COILOSTEGA Levinsen, 1909. 



The parietal muscles are attached to the ectocyst and traverse the chitinons or 

 partially calcified cryptocyst 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 : 



Opesiulidae Jullien, 1888. 



Subfamily Microporidae Hincks, 1880. 



Onychocellidae Jullien, 1881. 



Lunulariidae Levinsen, 1909. Kfr^--opie 



Aspidostomidae Canu, 1908. 

 Steganoporellidae Levinsen, 1909. FIG. 54. Structure of the Coilo- 



Thalamoporellidae Levinsen, 1909. stega. 



Setosellidae Levinsen, 1909. Diagrammatic transversal section 



Chlidoniidae Levinsen, 1909. of a zooecium of the t'oiloste S a. 



A1 . ,.. -. T . (After Harmer, 1902.) cri/pt, calci- 



Alysidudae Levinsen, 1909. ^ed cryptocyrt; ect, membranous 



ectocyst; ople, opesiule containing 



Family OPESIULIDAE Jullien, 1888. 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 OnycTiocella 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 



