10 
forms referred to this group is very difficult. In my paper of 1911, 
I published my investigations on the shape and development of the 
operculum in the genera Stegopoma, Cuspidella, Lafoéina, Caly- 
cella and Tetrapoma. I showed that the operculum of the three 
first mentioned genera is quite another thing than the operculum 
of Calycella and Tetrapoma, in which it is a transformation of the 
original roof of the young hydrotheca, while the operculum of Stego- 
poma, Cuspidella and Lafoéina takes origin from the uppermost 
part of the sidewall of the hydrotheca. It would be very desirable 
to obtain such investigations in the other genera of Campanulinidæ 
especially in the different species of the genus Campanulina (see 
below). — Levinsen mentions the different types of operculum 
within the "Campanulinidæ”, and points out "the significant pheno- 
menon that a number of different forms independently and in different 
manner have developed a protecting roof to the hydrotheca" (1. Cc. 
p. 293). The consequence must be, I think, that the "family” 
Campanulinidæ is a heterogeneous sample of genera, only kept 
together by the presence of an operculum, but there is no reason 
at all to base a relationship between two or more forms on the pre- 
sence of opercula of quite different origin. — The ”Campanulinidæ”, 
as defined by Levinsen, must be separated into several parts. 
Above is mentioned that 7oichopoma must be placed near Lafoéa. 
The new genus Abietinella Levinsen with the species Abietinella 
fZygophylax) operculata (Jåderholm) which has been dealt with 
thoroughly by Levinsen has its nearest relatives among the 
Lafoéidæ such as Zygophylax and Lictorella, indicating a transition 
to the Sertularidæ from the Lafoéidæ, not from the Campanulinidæ. 
The operculum of Abietinella has no resemblance to any operculum 
within the Campanulinidæ. On the other hand, as Levinsen 
himself points out, there are many resemblances between Abietinella 
and the above mentioned genera of Lafozidæ, it must, therefore, 
be placed within this family in spite of the presence of an operculum. 
The remaining genera of Campanulinidæ fall into two main- 
groups, according as the operculum takes origin from the roof or 
