NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
213 
Variations . — The specimens from Jackson. Mississippi, have the zooecia very 
distinctly marked, because they are separated by a thin and salient thread, which 
gives them a particular aspect very difficult to define. In the other localities the 
zooecia are united among themselves and quite indistinct, giving these specimens a 
very different appearance. Nevertheless, the other characters are identical. 
The onychocellarian opesium is a little longer than that of the zooecium, 
but the character is not evident at first glance because of its slight width. 
The fusion of the distant canal of the onychocellarium with the cryptocvst of 
the distal zooecium is not general 
and the extreme point of this organ 
is often distinct without ever being 
prominent. 
Affinities. — The difference be- 
tween this species and Rectonycho- 
ceMa bilamellaria is almost entirely 
zoarial. Still, there are some slight 
zooecial differences; the opesium is 
elliptical, without an enlarged, 
straight or convex proximal border, 
and the length of the onychocel- 
larian opesium is a little greater than 
the opesium of the zooecium. 
The species differs from Rec- 
tonychocella tepuis in its smaller mi- 
crometric dimensions (Lz=0.45 mm. 
instead of 0.55 mm.) and in its ony- 
chocellarian opesium which is smaller 
and more tapering below. 
Occurrence. — Upper Jacksonian 
(Ocala limestone) : Bainbridge, Geor- 
gia (rare) ; Chipola River east of 
Marianna, Florida (rare) ; West 
Bank Sepulga River, Escambia County, Alabama (rare). 
Cotypes .- — Cat. Nos. 63969, 63970, U.S.N.M. 
Genus VELUMELLA, Canu and Bassler, 1917. 
1917. Velumella Cantj and Bassler, Synopsis of American Early Tertiary Cheilostome 
Bryozoa, Bulletin 96, United States National Museum, p. 26. 
The retractor muscles of the polypide are attached in the median axis of the 
zooecium; the opesiular indentations are symmetrical. The onychocellaria are 
straight, without distal canal; the rachis of the mandible bears two broad mem- 
branes; the opesium of the onychocellarium is elliptical and entirely denticulated. 
Fig. 58. — Genus Velumella Canu and Bassler, 1917. 
A-D. Velumella ( Onychocella ) levinseni Canu and 
Bassler, 1917. A. A group of zooecia, the two upper- 
most with ovicell, X 40. B. A zooecium with 
ovicell(oi>). In the covering membrane of the aper- 
ture is seen a simple chitinized operculum, and in 
each of the two sinuses of the aperture is the end of 
a parietal muscle, X 55. C. A zooecial operculum 
above which there is an ooecial operculum, X 75. 
D. Avicularian mandible, X 40. 
