NORTH AMERICAN EARLY TERTIARY BRYOZOA. 443 



The ovicell is globular, salient, with trcmopores analogous to those of the 

 frontal (fig. 5) ; the zooecia which bear them have also an avicularium and a 

 spiramen, bu the latter invariably becomes closed and it does not appear in vertical 

 sections (fig. 15). The ovicell is enormous, almost as large as the zooecia (fig. 15). 

 If it contains only larvae, as is probable, their expulsion through a peristomice 

 so small would present some difficulty. 



Tangential sections (figs. 13, 14) show numerous tremopores; the reticulations 

 are not visible on account of the distance of the olocyst. 



Affinities. This species differs from Metradolium labratulum in the absence 

 of the large oral labruin. 



It differs from Mctradol/n/n pan>irimulatum in the rarity of the zooecia with 

 rimule-spiramen, in the much smaller dimensions of the peristomice (0.12 instead 

 of 0.14mm.), and in the constant presence of the large oral avicularium. 



Occurrence. Middle Jacksonian: Wilmington, North Carolina (very com- 

 mon) ; Eutaw Springs, South Carolina (rare.^ ; near Lenuds Ferry, South Caro- 

 lina (common) ; Rich Hill. Crawford County, Georgia (common) : 12 miles south- 

 east of Marshallville, Georgia (rare) ; 3 miles south of Perry, Georgia (very com- 

 mon). 



Cotypes.CaL No. 62596, U.S.N.M. 



METRADOLIUM PARVIRIMULATUM, new species. 



Plate 55, figs. 15-20. 



.Description. The zoarium is free, compressed, bilamellar ; the fronds are flat, 

 narrow, bifurcated; the lamellae are inseparable. The zooecia are little distinct; 

 the frontal is convex, thick, formed of a tremocyst with numerous tubules. The 

 apertura (interior) is semilunar; the peristomice is small, transverse; it bears a 

 small unsymmetrical rimule-spiramen. one side being higher than the other; the 

 peristomice of the zooecia with spiramen is wide, elliptical, transverse. There are 

 two symmetrical, oral avicularia, of which one is much larger than the other; the 

 latter is salient, elliptical, the beak turned toward the exterior. 



Measurements. Peristomice 1, 



. upe=0.1-2mm. Zooecia .3=0.56-0.60 mm 

 (exterior) J 



'Variations. The principal avicularium is very small (fig. 17), medium sized 

 or very large (fig. 19). The zooecia with spiramen are rare; they are arranged 

 in groups in the midst of the others. AVe are unable to learn what influence causes 

 their formation. The ovicell is unknown. 



Affinities. Tliis species differs from Mct/'iiJolhim ///xt/inUe in the rarity of 

 its zooecia with spiramen and its much smaller micrometric dimensions 

 (lz= 0.56-0.60 and not 0.74-0.76111111.1 . 



The specimens unprovided with zooecia with spiramen are difficult to dis- 

 tinguish from Metradoliwm ol>li'imtm. It differs from it in its smaller micrometric 

 dimensions (^=0.56-0.60 and not 0.70-0.80 mm.), in its much smaller rimule, 

 nearly symmetrical and not oblique. 



