96 
BULLETIN" 106, UNITED STATES NATIONAL MUSEUM. 
Occurrence. — Midwayan (Clayton limestone) : One mile west of Fort Gaines, 
Georgia (rare) ; Luverne, Crenshaw County, Alabama (rare). 
Eolotype.— Cat. No. 63790, U. S. N. M. 
MEMBRANIPORINA SINESOLUM, new species. 
Plate 19, fig. 5. 
Description. — The zoarium incrusts oysters; the zooecia are grouped in linear, 
axial series, emitting laterally zooecia arranged in quincunx. The zooecia are 
distinct, elongated, elliptical or oval, separated by a deep furrow; the gymnocyst 
is very small, inconstant, smooth, convex; the mural rim is very thin, flat, slightly 
enlarged at the base. 
Measurements. — Opesium 
Ad = 0.40 mm. 
lo— 0.20 mm. 
Zooecia 
\Lz= 0.44—0. 50 mm. 
(73=0.30 mm. 
Affinities.— This species has the simplicity of structure of M embraniporina 
laxa Reuss 1869 ; there is no basal olocyst , or, better, it is of extreme tenuity and 
the substratum is entirely visible. M. sinesolum differs, however, in its smaller 
dimensions (Ad= 0.40 mm. and not 0.50 mm.) and in its more regular zooecia. 
This is perhaps BifLustra lacroixi Smith 1872, which was incorrectly deter- 
mined. However, we are unable to make comparisons, as we have not discovered 
the recent species or measured the types. 
Membranipomna sinesolum differs from Membranipora capillimargo Canu, 
1911, from the Rocanean of Argentina, in its larger micrometric dimensions 
(£.3=0.44-0.50 mm. and not 0.35-0.42 mm.). Menibraniporina laxa Reuss 1869, 
M embraniporina capillimargo Canu, 1911, Biflustra lacroixi Smitt, 1872 and Mem- 
braniponna sinesolum , new specis, form a natural group of very great simplicity 
of structure. Unfortunately Ave lack recent specimens for study. 
Occurrence. — Lower Jacksonian (Moodys marl) : 24 miles north of Robert, 
Newton County, Mississippi (rare). 
Eolotype'— Cat. No. 63876, U. S N. M. 
MEMBRANIPORINA LAXA Reuss, 1869. 
Plate 13, fig. 16. 
1864. Membranipora subtilimargo Reuss, Ueber Anthozoen imd Bryozoen des Mainzer 
Tertiarbeckens, Sitzungsberiehte der k. Akademie der Wissenehaften, AVien, vol. 50, Abth. 1, 
p. 630. pi. 9, fig. 5. 
1869. Membranipora laxa Reuss, Die fossilen Anthozoen und Bryozoeu der Schiekten- 
gruppe von Crosaro, Denkschriften der k. Akademie der Wissenschaften, AVien, vol. 29, Abth. 
1. p. 252, pi. 36, fig. 14. 
1904. Membranipora laxa Canu, Exploration scientifique de la Tunisie, Etude des 
Bryozoaires tertiaires, p. 17, pi. 34, fig. 18. 
Affinities . — The figured specimen, which is the only one collected, is only 
moderately Avell preserved, but it presents some interesting peculiarities. There is 
no dorsal olocyst, the substratum is visible in the opesium, and the calcification is 
