140 
BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 
Genus LARNACIUS Norman. 1903. 
1903. Larnacius Norman, Notes on the Natural History of Bast Finmark, Annals and Maga- 
zine Natural History, ser. 7, vol. 12, p. 87. 
This genus differs from Amphiblestrum Gray, 1848, first in the interzooecial 
avicularium with pivot, second in the absence of dietellae, third in the distal end of 
the zooecium, which is divided into chambers by means of a transverse and usually 
one or two vertical connecting bars. The ovicell ap- 
pears closed by the operculum. 
Genotype.- — Larnacius ( Membranipora ) corniger 
Busk. 1852. Recent. 
The genus Larnacius mat' belong to a distinct family. 
SECTION IV. OVICELL NEVER CLOSED BY OPERCULAR 
VALVE. 
The ovicell is widely open above the operculum and 
the opesium. In the fossil forms the distal part of the 
mural rim is visible and not modified; the distal 
cicatrix left by the broken ovicell on the superior 
zooecium is shallow. In the recent species this kind 
of ovicell is closed by a vesicle which retracts or dilates 
by means of special muscles to facilitate the departure 
of the larvae or the entrance of the eggs. 
In the recent dry specimens the orifice of the ovicell 
appears simply closed by the ectocyst which always 
covers this structure. 
Levinsen in his “ Studies on the Cheilostomatous 
Bryozoa ” classes all the species of this group in the 
single genus Callopora Gray, 1848. We believe with 
Norman that the presence, the form, and the position 
ve for the establishment of natural although less impor- 
Genus ALDERINA Norman, 1903. 
Fig. 34. — Genus Larnacius Nor- 
man, 1903. 
Larnacius corniger Busk, 1852. 
Several zooecia, highly magni- 
fied, one with ovicell and the 
others with chambers in the 
place usually occupied by an 
ovicell. (After Norman, 1903.) 
of the avicularia may ser 
tant generic divisions. 
1903. Alderina Nokman, Notes on the Natural History of East Finmark, Annals Maga- 
zine Natural History, ser. 7, vol. 11. p. 596. 
Front wall entirely membranous, side Avails usually crenulated; no lateral 
spines. No avicularia, but nodulous processes sometimes developed in different posi- 
tions on the side of the zooecium. Ovicell usually bearing (either a rib or) a de- 
pressed area in front. Dietellae in the type, two pairs of lateral and two distinctly 
marked and separated distal. As in Ellisina. the two front pairs of dietellae 
usually extend outside the lateral walls, and the two posterior inside. (Norman, 
1905).' 
Genotype. — Alderina ( Membranipora ) imbellis Hincks, 1860. 
Range. — Senonian-Recent. 
