NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
557 
different from the lateral areolae. The peristomice is irregular, pyriform, the 
narrowest part below ; the peristome is thick ancl complete ; the peristomie is shal- 
low, but it hides the real form of the aperture which (seen from the interior) is 
elongated and elliptical. On the line of the areolae, in the vicinity of the peri- 
stomice, there is a small, simple, elliptical avicularium somewhat pointed. 
Measurements. — Aperture \ha~0.10 mm. 7 . [Zs=0.55-0.65 mm. 
(interior) l7u=0.07 mm. -jooecia j ^=0.25 mm. 
A-ffinities. — The frontal pores and the avicularia are quite variable. 
This species is very close to M eniscopora ( Eschara ) semitubulosa Reuss. 1869, 
of the Priabonian of the Vicentin. Unfortunately the latter has not yet been 
found again and no direct comparison is therefore possible. 
Occurrence.— Vicksburgian (Ryram marl) : One-fourth mile west of Wood- 
ward, Wayne County, Mississippi (common). 
Cotypes. — Cat. No. 61515, U.S.N.M. 
Genus BRACEBRIDGIA MacGillivray, 1886. 
1886. Bracebridgia MacGillivray, Descriptions of new or little known polyzoa, part 9, 
Transactions Royal Society of Victoria, p. 8. 
(Syn. Porostoma Cantt, 1907.) 
“ Zoarium bilaminate, erect. Apertura subcircular, straighter below, with 
an internal denticle; peristome thickened, smooth or with a small apiculate 
mucro; frequently in the fossils, but rarely in recent specimens, a triangular 
avicularium immediately below the lower lip; lateral avicularia on the free edges 
of the zoarium” (MacGillivray). The gonoecia are larger than the usual zooecia. 
The frontal is partially or totally covered over by a pleurocyst which is more or 
less confluent with the subjacent olocyst. 
Genotype. — Bracebridgia ( Porella ) emendata Waters, 1881. 
Ra,nge.- — Ja ckson i an — Recent. 
The genus Porostoma Canu, 1907, differs from Bracebndgia only in the 
place of the oral avicularium, which is placed entirely within the peristomie. Its 
function does not appear different, so it will be necessary to unite the two genera. 
The known species of Bracebridgia are as follows : 
Bracebridgia ( Porella ) emendata Waters, 1881, Miocene and Australian waters. 
Bracebridgia ( Porina ) subsvlcata Smitt. 1872. Recent, Florida. 
Bracebridgia ( Eschara ) polymorphic Reuss, 1864. Tongrian. 
Bracebridgia ( Eschara ) ignobilis Reuss, 1866. Middle Tongrian (=Rupelian). 
Bracebridgia ( Porostoma ) polymorphism Canu, 1907, not Reuss, 1869. (=/?. 
dentiferum- , name new) Ypresian. 
Bracebridgia incisum Canu, 1907. Ypresian. 
Bracebridgia ( Porostoma ) clavatum Gregory. Lutetian. 
Bracebmdgia ( Meniscopora ) subcrenulata Canu, 1907. Ypresian-Lutetian, 
Bartonian. 
