EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVINCES. 103 



pores irregularly angular, of variable size, sometimes nearly as large 

 as the zooecia, and frequently abundant enough to surround a zooe- 

 cium. They are most abundant in the maculae which are developed 

 at more or less regular intervals, but are not a conspicuous surface 

 feature. 



In tangential sections the thin-walled cells with the small, although 

 well developed, thick, crescentic lunarium form the important fea- 

 ture. Vertical sections show less important specific characters, 

 although here the generic characters are best illustrated. These are, 

 first, the ceramoporoid wall structure with small mural pores and 

 fine, transversely laminated tissue, and, second, the loose vesicular 

 structure formed by the mesopores. A few thin diaphragms occur 

 in the tubes. The vesicular structure is formed by the great irregu- 

 larity of the mesopore walls, allowing them at times to coalesce. 

 Sometimes an oblique or irregularly placed tabula occurs in the 

 mesopores and by its position increases the vesicular appearance. 



The small but sharply elevated lunarium externally, and the loose, 

 vesicular internal structure, are diagnostic of the species. 



Occurrence. — Apparently common in the Kuckers shale (C2), Baron 

 Toll's estate, near Jewe, Esthonia. 



Holotype.—Csit. No. 57177, U.S.N.M. 



Specimens and thin sections in the collections of the British Museum. 



FAVOSITELLA DISCOIDALIS, new species. 



Text fig. 37. 



Cfr. Bythotrypa laxata Ulrich, Geol. and Nat. Hiso. Surv. Minnesota, vol. 3, pt. 1, 

 1893, p. 325, pi. 28, figs. 21-25. 



Zoarium a small, discoidal mass, with a concentrically wrinkled 

 epitheca on the flat basal side, and the upper surface slightly convex. 

 None of the specimens examined exceeds 20 mm. in diameter and 

 6 mm. in height. The zooecial apertures open directly at the sur- 

 face, are large, nearly equal in size, and range in shape from subovate 

 to obscurely polygonal. An average single zooecium is 0.6 mm. in 

 diameter, with three usually occurring in 2 mm. The lunarium, 

 although clearly developed and occupying nearly one-fourth of the 

 zooecial circumference, overarches the aperture but slightly. Meso- 

 pores few for the genus, the number shown in the accompanying 

 illustrations (figs. 37 c, d) being the maximum seen. Seldom do the 

 mesopores attain the size of the zooecia from which they can always 

 be distinguished when almost as large, by the absence of a lunarium. 

 As in other species of the genus, the mesopores, at more or less regular 

 intervals, cluster together and form maculae, which, however, in the 

 present form, are small and inconspicuous. 



In tangelitial sections the zooecia are seen to vary from subangular or 

 polygonal to subovate in outline, their shape being determined by the 



