NORTH AMEEICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 207 



heights, separated by a thick continuous cuticle; the orifice is polygonal with 

 salient peristome. The ovicell is large, irregular, surrounding a score of tubes. 



Variations. — The form of the zoarium is quite variable, but it is always a small 

 globular mass simple or mammillated. It grows either on shells or on algae. The 

 small pores observed on the surface of the zoarium are not mesopores but are young 

 tubes in process of formation. The diameter of the normal apertures varies from 

 0.12 to 0.15 mm. 



In longitudinal section the zooecial walls are not vesicular; they show a long, 

 minute canal corresponding to the disappearance of the cuticle which surrounded 

 the tubes on a living specimen. 



Affinities. — ^This species differs from Tretocycloecia tortilis Lonsdale, 1845, in 

 its nonarborescent zoarial form, in the smaller zooecial diameter, and in its larger 

 ovicell. 



Occurrence. — Pliocene (Waccamaw marl) : Waccamaw River, Horry County, 

 South Carolina (very rare) . Miocene (Duplin marl) : One-half mile above Eden- 

 house Point, Chowan River, and 10 miles south of Greenville, North Carolina (rare). 



Cotypes.—C&t. Nos. 68756-68757, U.S.N.M. 



Genus PSILOSOLEN Canu and Bassler, 1922. 



1922. Pdlosolen Canu and Bassler, Studies on Cyclostomatous Bryozoa, Proc. U. S. National 

 Museum, vol. 61, p. 112. 



There are no adventitious tubes. The tubes are cylindrical with peripheral 

 gemmation. 



Genotype. — Psilosolen capitiferax, new species. 



Range. — Pleistocene, Recent. 



The ovicell is a swelling perforated by the tubes as in the Diaperoeciidae, but 

 it is not inserted in the tubes themselves. On the contrary, the ovicell is per- 

 pendicular to the tubes and surrounds only the peristomes as in the family Tre- 

 tocycloeciidae, where this new genus may be naturally classed. The ovicell is 

 little convex and very different from the elongated and very salient sac of the 

 Ascosoeciidae. 



It is remarkable to note again that through the geological ages it is the simplest 

 form of the family that has persisted. The Cretaceous and Tertiary genera of this 

 family are provided with adventitious tubes. 



PSILOSOLEN CAPITIFERAX. Canu and Bassler, 1922. 



Plate 44, figs. 11-21. 



1922. Psilosolen capitiferax Canu and Bassler, Studies on Cyclostomatous Bryozoa, Proc. TJ. S. 

 National Museum, vol. 61, p. 112, pi. 13, fig. 8. 



Description. — The zoarium is free, with the form of Entalophora, more or less 

 compressed, dichotomous; the extremity of the branches is enlarged, flattened, and 

 hears the ovicell. The tubes are visible, separated by a furrow, convex, wrinkled 

 transversely, somewhat widened at the summit; the peristome is thin, salient, 

 elliptical or suborbicular. The ovicell is a swelling covering the extremity of a 

 branch; it is perforated by a dozen tubes, some of which are closed by a finely porous 

 diaphragm. 



