NORTH AMERICAN EARLY TERTIARY BRYOZOA. 



403 



shelter from extraneous influences. The orifice of this chamber is irregular; it is 

 not a peristomice, since it has no pcristome. The tentacles must necessarily be 

 long and flexible. 



The locclla is the equivalent of the peristomie ; it assumes the same functions 

 with great economy of calcification. 



cal mi 



F ,85 G "23 



E >> T ,210 H 



FIG. 118. Anatomy ( the I'eri.stomellae Canu and Bassler, 1917. 



A-G. PeristorneUa coccinea Abildgaard, 1805. A. Free larva seen in profile, showing the 

 slightly exposed disposition of the corona and the relatively small size of the terminal bud, 

 X 75. B. Free larva, oral face, X 50. C. Free larva, aboral face, X 50. (A-C after Barrois, 

 1877.) cal. calotte (terminal bud): CO, digestive cavity: fl, flngellum ; mi, aboral ruesoderm; 

 ins, oral (labial) mesoderm ; oc, oculiform points; pl\, pharynx; PI, vibratile plume; RV, border 

 of the calotte. D. Zooecia, X 30. (After Hincks, 1880.) E. Operculum, X 85. (After 

 Waters, 1878.) F. Mandible, X 85. (After Nordgaard, 1904.) G. Avicularian mandible, X 

 23. (After Waters, 1885.) 



H. Pcrixtouiella prestans Hincks, 1882. View from the basal surface showing dietellae, X 

 23. (After Levinsen, 1909.) 



I. Exochella Imiyirostris Jullien, 1SSS. Polypide seen anteriorly, X 210 ; the aviculariurn 

 has been drawn at its place ; its muscular fibers are erect. The feeble development of the 

 stomach is to be noted. (After Jullien, 1888.1 est, stomach -^int, intestine (?) ; mav, elevator 

 muscles of the avicularian mandible; mo, opercular muscles: nir, large retractor muscles of 

 the polypide ; oes, esophagus ; ph, pharynx. 



The principal genera of this group are : 

 BathoseHa Canu and Bassler, 1917. 

 jRomanch-eina Jullien, 1888. 

 PeristorneUa Levinsen, 1902. 



