396 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



distinct, elongated, elliptical; the frontal is convex and formed of a thick tremocyst 

 with large tubules resting on a very thin perforated olocyst. The aperture is 

 elliptical, somewhat elongated; the anter is separated by two very small cardelles 

 from a poster somewhat smaller. The avicularium is long, thin, provided with a 

 pivot; it is placed laterally under the aperture; the beak is falciform. The old 

 zooecia are indistinct. 



fAa=0.15mm. . <Ls= 0.60-0.70 mm. 



Measurements. Aperture 7 Zooecia' //. o- 



lZa=0.12 mm. 1 Zs=0.30-0.3u mm. 



Affinities. Only the two figured specimens have been found; apparently the 

 proliferation of this species does not correspond to the zoarial vigor. In the old 

 zooecia the tubules are very long; the avicularia immersed between them are hardly 

 visible. 



The species differs from Hippodiplosia vcspertilio in the presence of its large 

 falciform avicularium, which attains a length of 0.35 mm. 



Occurrence. Middle Jacksonian (Castle Hayne limestone) : Wilmington, North 

 Carolina (very rare). 



Cotypes.Cat. No. 64096, U.S.N.M. 



HIPPODIPLOSIA MAGNIPOROSA, new species. 



Plate 87, figs. 7-9. 



Description. The zoarium is hollow, cylindrical, branched, unilamellar, rarely 

 plurilamellar ; it incrusts small algae. The zooecia are little distinct, elongated, 

 almost cylindrical ; the frontal is a tremocyst with large funnel-shaped pores rest- 

 ing on an olocyst perforated by small corresponding pores. The aperture is almost 

 orbicular and formed of a large anter separated from a small concave poster by 

 two very salient, triangular cardelles; the peristome is often very wide, smooth, 

 and very little salient. The ovicell is embedded in the distal zooecium, it is 

 hyperstomial and opens above the aperture by a thin slit; it is of the same 

 nature as the frontal. Often the coalescence of two tremopores determines the for- 

 mation of a small lateral avicularium with pivot. 



[Aa=0.20mm. . r 7,3=0.75 mm. 



Measurements.- Aperture {, n .. ., Zooecia ^ , , 



\h=OAOmm. 



Variation*. The lateral avicularium is very inconstant. The young zooecia 

 (fig. 7) have a thin peristome, somewhat prominent in front. Sometimes the 

 tremocyst is detached from the underlying olooyst (fig. 9). 



Affinities. This species differs from Hippodiplosia petiolus Lonsdale. 1845, 

 in its hollow zoarium and its shorter zooecia. 



It differs from Hippodiplosia stranqulata in its shorter aperture and in the 

 absence of a peristomial avicularium. 



Occurrence. Vicksburgian (Marianna limestone) : Salt Mountain, 5 miles 

 south of Jackson, Alabama (rare). 



Vicksburgian (Red Bluff clay) : Seven and one-half miles southwest from 

 Bladen Springs, Alabama (rare). 



Uotypes.Czt. Nos. 64278, 64279, U.S.N.M. 



