EAKLY PALEOZOIC BEYOZOA OP THE BALTIC PEOVINCES. 89 



both at the surface and in tangential sections, by the fact that the 

 lunaria are directed away from their centers. The zooecia are 

 arranged in somewhat curved series about the maculae, but this regu- 

 larity is obscured by the usually irregular shape of the apertures. 

 The latter may be said to be irregularly rhomboidal in outline as a 

 rule, with a small but very distinct crescentic lunarium at the proxi- 

 mal angle. With the introduction of an occasional mesopore, the 

 rhomboidal shape is destroj^ed and an irregularly angular aperture 

 results. Zocecial walls thin. Lunaria small, crescentic, with the 

 ends projecting into the zocecial cavity. Mesopores more numerous 

 than usual in the genus, averaging about one to every four zooecia. 



In tangential sections the shape of the zooecia and the small, dis- 

 tinct, crescentic lunaria are the salient features. Vertical sections 

 show very simple zocecial tubes without tubule and with walls exhib- 

 iting the loose porous structure of the ceramoporoids. 



The difference between this and the preceding species has been 

 mentioned under the description of the latter. No other incrusting 

 Russian Ordovician bryozoan has so distinct a lunarium, so that this 

 character alone will aid in the recognition of C. lunatifera. 



Occurrence. — Rare in the Wesenberg limestone (E) at the quarries, 

 Wesenberg, Esthonia. 



Holotype.—Ca,t. No. 57199, U.S.N.M. 



One specimen and a thin section of the type-specimen are in the 

 collections of the British Museum. 



CREPIPORA INCRASSATA, new species. 

 Text fig. 28. 



Zoarium massive, the type and only specimen being of an irregular, 

 discoidal shape, 13 mm. at its greatest height, and 40 mm. in its 

 longer diameter, composed of four superimposed layers of zooecia. 

 The upper celluliferous side is slightly convex, v/hile the lower side, 

 which is uneven and somewhat wrinkled, shows either the bases of 

 the zooecia or their basal covering forming the epitheca. The cellu- 

 liferous surface is smooth and bears maculae of mesopores, which, 

 although inconspicuous to the eje, are readily seen with a lens or in 

 thin sections. The zocecial apertures open upon the surface directly, 

 are polygonal in outline, have comparatively thick walls, with their 

 proximal fourth elevated and slightly arched over the cavity. This 

 overarching portion, the lunarium, is not distinctly separated from 

 the rest of the wall as in other species of the genus. An average 

 zooecium is 0.4 mm. in diameter but counting from a macula and 

 including the larger zooecia next to the cluster of mesopores, four and 

 one-half zooecia may be measured in 2 mm. Mesopores are present 

 but are confined to the maculae exclusively. 



Willie the massive growth, large, thick walled, direct zooecia, with 

 broad, rather indefinite lunaria, are sufficient to recognize this species, 



