NORTH AMERICAN EARLY TERTIARY BRYOZOA. 
231 
Rosseliana with clearly marked and constant opesiules. M embranipora ogivalh 
Seguenza 1879 is classed in this genus. 
Genus DACRYONELLA Canu and Bassler, 1917. 
1917. Dacryonella Canu and Bassler, Synopsis of American Early Tertiary Cheilostome 
Bryozoa, Bulletin 96, United States National Museum, p. 28. 
The polypidian convexity protrudes very little and is inconstant. The 
opesiules are large, round, lateral indentations. The ovicell is endozooecial. There 
are no opesial processes (therefore an opercular valve) . The opesium is elongated 
(therefore the parietal muscles are much developed). The avicularia are very 
small, constant, placed in all the interzooecial angles, and have the form of small 
tear drops. 
Genotype.- — Dacryonella octonaria Canu and Bassler, 1917. Jacksonian. 
This is a Rosseliana ornamented with avicularia. As in this genus also, the 
opesiules are inconstant and placed very far from the aperture in consequence of 
the great development of the parietal muscles. 
DACRYONELLA OCTONARIA Canu and Bassler, 1917. 
Plate 36, figs. 9-20. 
1917. Dacryonella octonaria Canu and Bassler, Synopsis of American Early Tertiary 
Cheilostome Bryozoa, Bulletin 96, United States National Museum, p. 28, pi. 3, fig. 4. 
Description. — The zoarium incrusts small shells or more often creeps over 
algae; very frequently it consists of many superposed lamellae. The zooecia are 
somewhat elongated, confluent among themselves, vaguely polygonal; the mural 
rim is broad, especially below, flat, smooth, oblique. The cryptocyst is terminated 
distally in a small polypidian convexity. The avicularia are straight, interopesial, 
triangular, projecting chiefly at the point. 
Measurements. — Opesia of large zooecia! mm ' 
L ° uo— 0.14 mm. 
Large zooecia ( Ls=0A0 mm. 
{ /s=0.30-0.40 mm. 
Opesia of r /?o=0.18 mm. 
small zooecia [Zo=0.10mm. 
Small zooecia 
1-2=0.40 mm. 
12=0.30 mm. 
Variations and affinities. — The polymorphism of this species is very remarkable. 
On the same zoarium, without apparent reason, the zooecia are considerably in- 
creased in size, chiefly at the extremity of the fronds. The larger zooecia are 
always grouped together, none of them being isolated; then their opesium becomes 
transverse and almost triangular. 
The polypidian convexity is here symmetrical, but as usual is not constant. 
However the proximal border of the opesium is nearly always straight or convex 
and very rarely concave. We know that this phenomenon may be observed in 
other genera of different families and that it can not serve as a generic character. 
