170 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
oblique, thin clistally, much enlarged and transformed into a cryptocyst proximally ; 
the gymnocyst is little convex and smooth. The opesium is anterior, elliptical, 
entire. The avicularium occupies the surface of the gymnocyst; it is large, salient, 
and terminated like the beak of a duck, with spatulate mandible. 
Measurements . — Opesiai 
4(9= 0.35-0.40 mm. 
?<9= 0.17 mm. 
Zooecia 
fZs=0.85-1.00 
l7s=0.35 mm. 
mm. 
Affinities . — The figured specimen is the only one that has been found and it 
unfortunately has no ovicell. The large avicularium is not constant, although 
many of the zooecia are unprovided with them; their presence is therefore not 
necessary to each zooecium. We think that the function of the avicularia, like 
that of the vibracula, is rather zoarial. 
Among the species of the same genus this is the only one in which the crypto- 
cyst is much developed; its relationships with the genus Amphiblestrum are there- 
fore close; but in the latter there is no gymnocyst and the avicularia are lodged 
in the interzooecial angles. 
The disposition of the zooecia is also much less regular than in the other 
species of Stamenocella. It differs from Stamenocella grandipora in its small 
opesiai length (0.35 instead of 0.50), its cryptocyst, and chiefly in its large avicu- 
larium in the shape of a duck’s beak. 
Occurrence . — Lower Jacksonian (Moodys marl) : Jackson, Mississippi (very 
rare). 
Holotype. — Cat. No. 63937, U.S.N.M. 
STAMENOCELLA PYRIFOKME. new species. 
Plate 30, figs. 13-16. 
Description . — The zoarium is bilamellar with narrow fronds; the two lamellae 
are back to back and separable. The zooecia are very long, narrow, distinct, sep- 
arated by a salient thread. The opesium is narrow, pyriform, the point toward 
the bottom, bordered by a collar. The cryptocyst is smooth, developed laterally 
and interiorly to the opesium. The ovicell is globular, salient, embedded in the 
cryptocyst of the distal zooecium; its orifice can not be closed by the operculum. 
The avicularium is small, salient, elliptical, provided with a pivot or two lateral 
denticles. 
Measurements . — Opesia 
j4o=0.32-0.35 mm. 
17(9=0.10-0.15 mm. 
„ . \Ls= 0.55-0.60 
Zooecia | fe=(U5 _ a20 
mm. 
mm. 
Variations . — The lateral zooecia have an elliptical and nonpyriform opesium 
(figs. 13, 14). On the very wide fronds there are many rows of these different 
zooecia. The avicularia of the lateral zooecia are much more prominent and ap- 
pear claw-shapecl (figs. 13, 14). 
When it is properly illuminated, the peculiar orifice of the ovicell is quite 
visible. It is large, placed above the opesium, and the opercular valve can never 
close it. 
