NOKTH AMERICAN EARLY TERTIARY BRYOZOA. 347 



more or less granular and complete is deposited on the frontal, chiefly in the vicinity 

 of the areolae. The aperture is semilunar; the proximal border is linear and bears 

 a narrow, linear rather long rimule; the peristome is salient; it surrounds the 

 aperture and its rimule and it bears anteriorly six hollow spines. The ovicell is 

 large, salient, elongated, of the same nature as the frontal; it is formed of a 

 smooth, orbicular callosity (olocyst) surmounted by a prominent collar, and by 

 areolae ; it is never closed by the operculum. The avicularium is triangular, long, 

 salient, placed laterally below the aperture and deforming the zooecia; it is 

 transverse or oblique ; its point to the outside. 



fAa=0.15mm. . \Li 0.45-0.50 mm. 



Measurements. Aperture-L Zooecia , 



\la-O.W mm. U2=0.30-0.40 mm. 



Variations, The avicularium is sometimes far removed from the aperture (fig. 

 13) ; it is transverse (fig. 13) or oblique (fig. 14). 



The part of the peristome which surrounds the rimule forms an elegant festoon 

 above the aperture. 



The pleurocyst and olocyst are closely united. The smooth zooecia are young 

 zooecia in which the subjacent olocyst is still visible. The pleurocystal calcification 

 operates according to rule, the areolae toward the aperture with the formation of 

 small, interareolar, incomplete costules. 



On the ovicell the calcification is more regular and finer ; the physiological use 

 of this structure is unknown ; the length is 0.25 mm. 



Affinities. This species differs from Lacerna hexagonal^ in its small dimen- 

 sions and the presence of the prominent festoon which surrounds the rimule. 



It differs from Lacerna seguenzai Eeuss, 1869, in the absence of the oral mucro, 

 and from Lacerna siissi Eeuss, 1869, in the place, the size, and the form of its 

 avicularia. 



Occurrence. Lower Jacksonian (Moodys marl) : Jackson, Mississippi (com- 

 mon). 



Cotypes.C&t, No. 64047, U.S.N.M. 



LACERNA HEXAGONALIS, new species. 



Plate 44, figs. 17-20. 



Description. The zoarium incrusts Orbitoides, bryozoa, and shells. The 

 zooecia are distinct, little elongated, hexagonal; the frontal is little convex, formed 

 of an olocyst more or less covered by a pleurocyst and surrounded by a line of 

 large areolae. The aperture is semilunar; the proximal border is linear and notched 

 by a narrow, linear, rather long rimule ; the peristome is salient, and surrounds at the 

 same time the aperture and its rimule forming exteriorly an oval peristomice ; 

 the peristome bears six large, hollow spines. The ovicell is large, salient, elongated, 

 of the same nature as the frontal ; it is formed of a circular callosity surrounded by 

 very small areolae and a thick, salient collar; it is often closed by the operculum 

 when the latter opens. The avicularium is long, thin, triangular, little salient, 

 disposed in the same manner as the zooecial walls, without pivot. 



