NORTH AMERICAN EARLY TERTIARY BRYOZOA. 837 



The mesopores are small, polygonal, separated by thick walls, grouped in trans- 

 versal zones, alternating with the zones of the peristomes, and (in section) with 

 vesicular walls and often ramified. 



Diameter of the peristome 0.14 mm. 



Diameter of the apertura.. _ 0.10 mm. 



Measurements. -p.- * 1. i_ i 



Diameter of the branches 4.00 mm. 



Diameter of the cancelli 0.06 mm. 



This species was noted in 1SS-2 l by Ulrich, who discovered the nature of the 

 tubes and mesopores of Zonopora. 



We have not discovered the ovicell, so our generic reference is quite doubtful. 

 The resemblance of this species to Zonopora ligcriensis D'Orbigny, 1853, has 

 caused us to classify it provisionally in our new genus. 



We know that the large zones of mesopores are formed by their branching; 

 but the latter appears to be rather irregular, so that the longitudinal sections are 

 always somewhat confused. 



Affinities. This species differs from Tretocycloecia reticrtlata in its somewhat 

 smaller micrometric measurements. 



Occurrence. Miclwayan (Clayton limestone) : Mabel vale, near Little Rock, 

 Arkansas (rare). 



Cotypes.C^t. No. 65261, U.S.X.M. 



POLYASCOSOECIA, new genus. 



The ovicell is globular, salient, spread between the fascicles whose length it 

 alignments, placed eccentrically on the frontal. The tubes are cylindrical, oriented, 

 short; they ramify into numerous mesopores on the frontal. The dorsal of the 

 zoarium is thick, with lamellar structure, and perforated by vacuoles bent 

 toward the base. 



Genotype. Polyascosoecia coronopus, new species. 



Range. -Eocene- Pliocene. 



Further remarks upon this new genus and a description of the genotype are 

 included in a study of the cyclostomatous bryozoa now in press. 



This genus differs from Plem-onea in which the ovicell is placed identically, 

 not only in the different nature of the ovicell, but in its cylindrical tubes. 



It differs from the genus ErL-i^nm n. equally provided with pores on the two 

 faces of the zoarium, in its ovicell placed laterally, and in its short cylindrical tubes. 



POLYASCOSOECIA JACKSONICA, new species. 



Plate 134, figs. 1-21. 



Description. The zoarium is free, bifurcated, or dichotomous, with triangular 

 section, often reticulated. The fascicles are very little salient, composed of four 

 tubes, arranged alternately on each side of the median crest and quite close to it. 



'1882. Journal Cincinnati Society Natural History, p. 143. 



