XORTH 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 SmiK, 1872. 



Plate 17, figs. 15-17. 



1872. Escharella rostrigera Sjiitt, Floridan Bryozoa, Kongl. Svenska Vetenskaps-Akademiens 



HandEngar, vol 11, p. 57, pi. 10, figs. 203-205. 

 1918. Hippaliosina rostrigera Canu, Hippaliosina, un nouveau genre de Bryozoaires, Bulletin de la 



Soci6t6 g^ologique de France, ser. 4, vol. 18, p. 89. 



Measurements (fossil specimens) : 



Apertura of ordi-fAa = 0.15 mm. ^ ,. . fL2 = 0.44-0.55 mm. 



• 7 r, 1 r, Ordinary zooecia , „ „_ 



nary zooecia-.lZa = 0.10 mm. •' [ te = 0.30 mm. 



Apertura of ovi-(/ia = 0.16 mm. r\ ■ ^^ j ■ fi2 = 0.50mm. 



11 1 • 1 /^,/./^,r, Ovicelled zooBcia , . „„ 



celled zooecia. Ua = 0. 16-0. 17 mm. [ lz = O.ZS mm. 



The oviceUed 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 oviceUed 

 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): Yorktowoi, 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.—G&i. No. 68681-6S6S3, U.S.X.M. 



Genus TREMOGASTERINA Canu, 1911. 



1911. Tremogasterina Canu, Iconographie des Bryozoaires fossiles de I'Argentino, 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. 



