NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
397 
HIPPODIPLOSIA BACCATA, new species. 
Plate 87, figs. 5, 6. 
Description . — The zoarium incrusts shells. The zooecia are short, little distinct ; 
the frontal is somewhat convex; it is formed of a tremocyst with widened pores 
surmounting an olocyst with very small pores; between the tremopores there are 
some very small pearl-like tuberosities. The aperture is somewhat oval, the point 
below; the peristome is wide, smooth, a little salient, complete. The ovicell is 
hyperstomial and very fragile. On the same peristome, and placed laterally, there 
is a small avicularium ( ?). 
M easurements. — Aperture 
l'a=0. 10 mm. 
/a=0.10mm. 
Zooecia 
i Lz= 0.30 mm. 
1/3=0.20 mm. 
Occurrence. — Vicksburgian (Bvram marl) : Byram. Mississippi (common). 
Vieksburgian (Red Bluff •clay) : Red Bluff, Wayne County, Mississippi 
(rare). 
Cotypes. — Cat. No. 61277, U.S.N.M. 
HIPPODIPLOSIA STRANGULATA, new species. 
Plate 87, figs. 10-13. 
Description . — The zoarium is unilamellar; it incrusts algae or shells. The 
zooecia are elongated, distinct, fusiform; the frontal is convex and formed of a 
thick tremocyst with large pores. The apertora is elliptical, quite elongated, a 
little constncted in its lower parts, and formed of a large anter, separated from a 
smaller poster by two salient carclelles; it is buried by the development of a small 
peristomie; the peristome is thin, salient, without spines. The ovicell is large, 
globular, salient, ornamented with pores somewhat smaller than those of the frontal ; 
it is hyperstomial, imbedded in the distal zooecium; it opens into the peristomie. 
Tn the peristomie itself or on the peristome there is a quite small orbicular avicu- 
larium. 
M easurements. — Apertura 
ha= 0.20-0.22 mm. 
la= 0.14—0.15 mm. 
Zooecium 
Ls= 0.70-0.77 mm. 
lz= 0.30-0.35 mm. 
Variations.-— The micrometric dimensions of this species vary much and are 
of little use; this is the habitual rule of species growing upon various kinds of sub- 
strata; there are some wide zooecia (fig. 11), some narrow zooecia (fig. 10) and some 
bordered zooecia (fig. 12). 
Exteriorly this species has the aspect of Porella; it has all the essential char- 
acters; tremocyst, peristomial avicularium and ovicell opening into the peristomie. 
The two carclelles alone reveal to us a different hydrostatic system. The reader 
may be convinced of this by consulting our anatomical tables of the Hippoporinae 
and Smittinidae and in comparing their compensatrices. Moreover, species of this 
sort have a chitinous operculum very different from the opercula of Smittinidae, 
as it is easy to observe, notably in Eschara lamellosa. The absence of the chitinous 
appendages and of the polvpide is often very unfortunate for the paleontologist. 
