NORTH AMERICAN LATER TERTIARY AND QUATERNARY BRYOZOA. 
167 
observed along the thirty-fifth and thirty-sixth parallels, the recent species has 
been dredged only nearer the Equator from the thirty-fifth to the tenth parallels. 
The emigration northward toward the Equator appears thus to be a phenomenon 
as real as in the other hemisphere. 
The bryozoa, on account of their method of life and their abundance in the 
marine currents, are generally rather cosmopolitan. It is remarkable that the 
genus Hippaliosina has been so sensitive to external variations, and this is a new 
phenomenon which merits recognition. 
HIPPALIOSINA ROSTRIGERA Smitt, 1872. 
Plate 17, figs. 15-17. 
1872. Escharella rostrigera Smitt, Floridan Bryozoa, Kongl. Svenska Vetenskaps-Akademiens 
Handlingar, vol 11, p. 57, pi. 10, figs. 203-205. 
1918. Hippaliosina rostrigera Canu, Hippaliosiua, un nouveau genre deBryozoaires, Bulletin de la 
, Societe geologique de France, ser. 4, vol. 18, p. 89. 
Measurements (fossil specimens): 
Apertura of ordi-(/i.a = 0.15 mm. „ .. . {Lz = 0.44-0.55 mm. 
nary zooecia(m = 0.10 mm. J [ 12 = 0.30 mm. \ 
Apertura of ovi-[Aa = 0.16 mm. . fL 2 = 0.50mm. 
celled zooecia. I ta = 0.16-0.17 mm. [ 12 = 0.38 mm. 
The ovicelled zooecia have an aperture larger and transverse and, moreover, of 
irregular form. Smitt has noted and has figured an elliptical aperture measuring 
0.36 mm. in width. This variation must be rather rare, for we have only observed 
it on the fossil specimens from the Miocene near Yorktown, Virginia. In 
the Australian species the small ovicelled zooecia appear to be absent. The ovicelled 
zooecia should not be confounded with gonoecia. The latter do not contain a 
polypide, as the ovary alone occupies the interior cavity. The ovicell is little 
salient, little visible, but always apparent on our fossil specimens. The zooecia 
which bear them are larger. 
This species has been dredged south of Florida in the vicinity of the Tropic of 
Cancer. The special location gives a clue to the contraction of the equatorial zone 
since the Oligocene period. 
Geologic distribution. —Miocene (Yorktown formation): Yorktown, Suffolk, 
and 3 miles southwest of Petersburg, Virginia (common). Miocene (Duplin marl): 
Natural Well, 2 miles southwest of Magnolia, Duplin County, North Carolina 
(common). Pliocene (Waccamaw marl): Waccamaw River, Horry County, South 
Carolina (rare). Pliocene (Caloosahatchee marl): Monroe County, Florida (rare). 
Habitat. —South of Florida at a depth of 56 to 59 meters. 
Plesiotypes.— Cat. No. 68681-68683, U.S.N.M. 
Genus TREMOGASTERINA Canu, 1911. 
t 
1911. Tremogasterina Canu, Iconographie des Bryozoaires fossiles de FArgentine, pt. 2, Anales 
del Museo Nacional de Buenos Aires, vol. 21 (sec. 3, vol. 14), p. 256. 
The ovicell is concealed. The frontal is perforated by a large pore and 
surrounded by a line of areolar pores. The apertura is semielliptical. Avicularia 
between the apertures. 
