EAELY PALEOZOIC BEYOZOA OP THE BALTIC PROVINCES. 271 



The large, rounded zooecia, distinct peristomes, solid interspaces, 

 and cjdindrical branches are characters which will readily distinguish 

 this species. Certain species of Hallopora have a similar zoarium and 

 general aspect, but their mesopores are never closed at the surface. 



Occurrence. — Kara in the Kuckers shale (C2) at Keval, and in the 

 Jewe limestone (Dl), Baron Toll's estate, in Esthonia. 



Holotype,—Csit. No. 57373, U.S.N.M. 



British Museum, thin sections of the type-specimen. 



TREMATOPORA CYSTATA, new species. 



Plate 11, fig. 25; text fig. 160. 



Numerous weU-preserved examples of this typical Httle Trema- 

 to^pora are in the collections before me, and all agree in the internal and 

 external features shown on plate 11, figure 25, and text figure 160. 



'GaQ% 



Fig. 160.— Teematopoea ctstata. a and h, two feagments, natxjeal size; c, tangentul section, 

 x20, showing oval zocecia, distinct peeistomes and small acanthopoees; d, seveeal zocecia, 

 x40; e, veetical section of a beanch, showing the usual appearance, x20. kuckees shale 

 (02), Reval, Esthonia. 



The zoa,rium is of small, cylindrical stems, 2 to 3 mm. in diameter, 

 which branch frequently and irregularly. The surface is smooth, but 

 has distinct maculae of larger zooecia and wider interspaces, as shown 

 in figure 25 of plate 11. Acanthopores are rather numerous, although 

 not as abundant as in Trematopora primigenia. Vertical sections 

 show the most decided features of internal structure, the presence of 

 abundant cyst-hke structures filling the mesopores. Near the sur- 

 face these are obscured or replaced by a dense, laminated tissue. 

 Six to seven zooecia occur in 2 mm. 



Trematopora cijstata is closely related to T. primigenia, but differs 

 in having large zooecia, less abundant acanthopores, and especially in 

 the numerous crov/ded, cyst-like diaphragms filling the mesopores. 

 Trematopora IcucJcersiana has larger zooecia, fewer acanthopores, and 

 a more robust zoarium. 



