172 BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
STAMENOCELLA INFERAVICULIFERA, new species. 
Plate 31, figs. 6-15. 
The zoarium is free with the two lamellae inseparable and growing back to 
back. The zooecia are elongated, distinct, narrowed in back; the mural rim is 
little salient, very thin, attenuate at its base. The opesium is elliptical or oval, 
entire; the gymnocyst is flat, smooth. The marginal zooecia have no avicularia. 
The ovicell is small, globular, fragile, placed on the gymnocyst of the distal 
zooecia, closed by the operculum. The avicularium is situated on the inferior por- 
tion of the gymnocyst in close contact with the mural rims of the proximal 
zooecium. 
M easurements . — 
#0=0.30-0.36 mm. 
lo= 0.10-0.16 mm. 
Zooecia 
[Zs=0.70-0.74 mm. 
\ls— 0.24-030 mm. 
V ' aviations . — This species is exceedingly variable and its study has required 
considerable effort; moreover it appears at several distinct horizons in the Jack- 
sonian and Vickburgian. The more perfect specimens shown in our figures are 
extremely rare; the avicularium here assumes a peculiar form without axis or 
pivot, which makes its nature doubtful. 
Figure 10 shows that on the same zoarium there may be extraordinary varia- 
tions. Here the broken ovicell appears to be quite voluminous and to crowd the 
avicularium close to the opesium. In specimens from Monroeville, Alabama, the 
proximal avicularium is smaller (fig. 14). In the course of weathering they become 
smaller and smaller (fig. 11), divide in two, and even may be replaced by a few 
punctations (fig. 13). 
The opesium is sometimes elliptical and sometimes oval. The two forms occur 
on the same specimen (fig. 7). 
The ovicell is quite variable in form and even in the same locality it is im- 
possible to find it of a constant size and shape. 
Affinities . — On certain rather well preserved specimens the avicularium is 
identical with that of StamenoceTla mecliaviculifera (figs. 7, 8), that is to say, it is 
of simple form with neither axis nor pivot. In only a single instance (fig. 12) have 
we observed a pivot which left no doubt as to the reality of this organ. 
Like the preceding species, S. inferaviculifera is found principally in the Jack- 
sonian although it is also common in the Vicksburgian. 
Occurrence . — Middle Jacksonian (Castle Hayne limestone) : Wilmington, 
North Carolina (very rare). 
Upper Jacksonian (Ocala limestone) : 9 miles north of Ocala, Florida (rare) ; 
Alachua, Florida (common). 
Vicksburgian (Marianna limestone) : 1 mile north of Monroeville, Alabama 
(common) ; Salt Mountain, 5 miles south of Jackson, Alabama (rare) ; west bank 
of Conecuh River, 1 mile below mouth of Sepulga River, Escambia County, Ala- 
bama (rare) ; Murder Creek, east of Castlebury, Conecuh County, Alabama (rare). 
Vicksburgian (Red Bluff clay) : One-fourth mile west of Woodward, Wayne 
County, Mississippi (rare). 
Cotypes.— Cat. No. 63941-63945, U.S.N.M. 
