330 Mr. H. Bekker on new Bryozoa 



brandies on my fragment are 2 mm. broad near the stem and 

 gradually get broader ; their normal width is 3 mm. ; the 

 zoarium is 1-1*5 mm. thick and elliptical in transverse 

 section. 



Zocecia are situated on both sides of the zoarium, but not 

 on its margins. On the surface the shape of the zocecia is 

 circular, sometimes one end of the aperture is slightly 

 narrower ; the zooecial apertures have a distinct peristome. 

 Transverse tp the axis of the zoarium, within 2 mm. are 5 

 zocecia. The transverse rows of zocecia, often sinuous, vary 

 in number from 4 to 6 within 2 mm. according to the size of 

 the interspaces. On the face of a zoarium 3 mm. wide in a 

 transverse row are 7-9 zocecia. The surface of the zoarium 

 between the zooscial apertures and on the margins is covered 

 with numerous minute granules (tig. 4.) 



A tangential section (fig. 5) shows in the greyish calcite 

 mass lighter, hexagonally shaped figures, with circular or 

 oval transverse sections of zooecial tubes, a little smaller than 

 the zocecial apertures on the surface of the zoarium. 



A transverse section (fig. 6) shows the zocecial tubes with 

 thin, light-coloured, narrow walls ; in the tubes are some 

 diaphragms; the tubes are a little larger on the surface than 

 in the interior of the zoarium. In the middle of the same 

 section are two layers of median tubuli, as seen iu transverse 

 section. 



Comparison tvith other Species o/ Pachydietya in Esthonia*. 

 — P. elegans always has elliptical zocecial apertures, with less 

 distinct peristome ; between the longitudinal zocecial rows 

 are distinct ridges, and the ends of the elliptical apertures are 

 also joined by ridges. P. fiahellum differs from P. elegans 

 and P. kuckersensis by its oviform zocecial apertures, and 

 from the latter by its ridges on the surface of the zoaiium. 

 P. cyclostomoides differs from all other species of Pachydietya 

 in its large zocecial apertures and in its granular ridges 

 between the zocecial rows. P. crassa differs strikingly from 

 P. kuckersensis in the distinct straight ridges between the 

 zocecial rows and in the shape of its zocecial apertures. 



Pachydietya crassa, Hall. (PI. VII. figs. 7, 8.) 



Stictopora crassa Hall, 1852, Nat. Hist. New York, Pal. ii. p. 45, 



pi. xviii. figs. 4 a-c. 

 Pachydietya crassa, Hall, Bassler, 1906, " Bryozoan Fauna of the 



Rochester Shale," Bull. U.S. Geol. Surv. cexcii. p. 57, pi. xviii. 



tigs. 11, 12, pi. xxi. tigs. 14-16. 



* See li. S. Bassler, 1911, "Early Paleoz. Bryozoa of the Baltic 

 Provinces," Bull. U.S. National Mus. lxxvii. 



