140 



BULLETIN 106, UNITED STATES NATIONAL MUSEUM. 



Genus LARNACIUS Norman, 1903. 



1903. Lnnwcius NOEMAX. Notes on the Natural History of East Finmark, Annals and Maga- 

 zine Natural History, ser. 7, vol. 12, p. 87. 



This genus differs from AmpMUc strum 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. Larn(n--nis (Membranipora ) corniger 



1852. Recent. 

 The genus Zamaciwsmay belong to a di-tim-t 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 C'heilostomatous 

 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 

 of the avicularia may serve for the e>tabli-hment of natural although less impor- 

 tant generic divisions. 



Genus ALDERINA Norman, 1903. 



1903. AMerina NORMAN, Notes on the Natural History of East Finmark. Annals Maga- 

 zine Natural History, ser. 7. vol. 11. p. 596. 



Front wall entirely membranous, side walls 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 Lllhuni. the two front pairs of dietellae 

 usually extend outside the lateral walls, and the two posterior inside. (Norman, 

 1905). 



Genotype. Aider! no (J)fcml>i-<ni!/-<ini \ nnlxll',* Ilincks, I860. 



Ranr/c. Senonian-Eecent. 



FIG. 34. Genus Larnaciits 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.) 



