273 
the hydrothecal margin and the operculum which Prof. Nutting 
believed he found in Sertularia desmoides Torr., and which he 
mentions in the following way: "No marginal teeth as a rule, but 
at times the margin has two obscure teeth.. Operculum usually of 
one flap attached to the abcauline side, others with two ill-defined 
flaps, and again there will be two flaps one above the other, both 
attached to the abcauline side.” 8. desmoides, of which Prof. 
Nutting has been so kind as to send me a number of. specimens, 
is a good Thujaria according to my definition of the genus, though 
it corresponds well to his definition of Sertularia. It has 'a quite 
similar aperture to that found in 7%. lichenastrum and Th. (Pasy- 
thea) acrodon, being provided with a freely prominent distal ad- 
cauline wall. In the specimens examined a number of hydrothecæ 
have been regenerated, and Prof. Nutting may have mistaken 
the freely prominent part of the new distal wall for an adcauline 
flap. The regeneration also explains the presence of two abcauline 
flaps one above another. 
In the key to the species the author mentions that three of 
the species, $. rathbuni, S. brevicyathus and S. flowersi are provided 
with a small median tooth. Such a tooth, however, is also' present 
in 8. pumila, and according to the author's figures also in $. 
mayeri, and S. cornicina.  S. rathbuni has not a three-flapped 
operculum; but the author has mistaken the angularly bent ad- 
cauline lip for two separate opercular valves. 
S. operculata, S. bispinosa and SS. pulchella belong to my 
new genus Odontotheca the definition of. which is given later. 
Thujaria (Flem.) Nutting. 
Only four of the twenty species named in Prof. Nutting's 
work, namely Tå. thuja, Th. polycarpa, Th. immersa and Th. lon- 
chitis belong to my genus Thujaria while 10 belong to Sertularia, 
and in two of these, Sert. tenera and Sert. robusta the author 
seems to have found inconstancy in the structure of the hydro- 
thecal margin and operculum. The named structures of S. tenera 
he mentions in the following way: "margin varying greatly, some- 
Vidensk. Meddel. fra den naturh. Foren, Bd. 64. 18 
