50 BULLETIN 16 5, UNITED STATES NATIONAL MUSEUM 



Measurements. — 



Zooecia \Lz= 0.54-0.63 mm. ZooeciajZs= 0.45-0.47 mm. 



(interior) ( Zs= 0.25-0.29 mm. (exterior) [fe= 0.21-0.27 mm. 



. f/ia=0.09mm. 



Apertura| fe=()07mm 



34 zooecia in 4 sq. mm on exterior lamellae, 22 on interior. 



Variations. — The strange variation, and one that has long disturbed 

 us, is the great difference in the measurements of the interior and 

 the exterior cells of the same multilamellar colony. The bilamellar 

 zoaria show the largest zooecia. The more the lamellae increase 

 in number, the smaller the zooecia become. This variation for a 

 long time caused us to believe that two species were included under 

 Morton's name. 



Structure. — The ovicelled zooecia have an internal and external 

 aperture of the same form and dimensions ; therefore, the opercular 

 valve closes the ovicell. There is no visible variation in the micro- 

 metric measurements of the aperture; therefore, the opercular valve 

 was strongly chitinous, perhaps detachable, and attached to an 

 ectocyst covering the entire zooecium. 



The apertural vibracula are very constant; rarely one of them is 

 lacking or changed in position; these are true zooecial organs abso- 

 lutely indispensable. The transverse section indicates that the basal 

 (median) lamella is not separable into two special lamellae. Fur- 

 ther, the successive lamellae are independent of one another. 



The large dimensions of certain fragments causes us to believe 

 that the entire colony was very large and that the entire development 

 of such a fragile ensemble could have occurred only in calm, deep 

 water. The zoarial base has not yet been discovered. 



Lang, 1921, has figured only the external zooecia. 



Occurrence. — Vincentown limesand : Very common at Timber 

 Creek and Mullica Hill and at Vincentown, N.J., not so abundant 

 near Blackwoodstown, N.J., and at Noxontown Millpond, Del. 



Plesiotyfe.— U.S.N.M. No. 73932. 



PLIOPHLOEA ELEGANS, new species 



Plate 12, Figure 8 



Description. — The zoarium is encrusting. The zooecia are dis- 

 tinct, separated by a deep furrow, elongated, elliptical, with elegant 

 aspect; the frontal is convex, bordered by small lateral tuberosities, 

 formed of 8 to 10 pairs of costules separated by lines of very small 

 lacunae; the costules are narrow, regular, granular; they begin at 

 the peripheral tuberosities and unite at the other extremity under 

 a small longitudinal crest. The apertural bar is thick, crescentic, 

 widest in the middle. The aperture is small, terminal, semielliptical, 



