102 Mr. D’Arcy W. Thompson on neio Hydroid 
theca. Hydrothecse barrel-shaped, strongly wrinkled, with a 
distinct neck, divergent for about half their length ; orifice 
with four teeth. 
Gonosome. Unknown. 
Locality. Brown’s River {Dr. Harvey). 
I have only a tiny scrap (‘2 inch in height) of the present 
species ; and owing to this circumstance, and considering also 
the contusion which still exists among the smaller Australian 
and New-Zealand species, I do not as yet assign it a name. 
The hydrothecas are singularly like those of S. tenella , 
Hincks, but are more immersed and much closer toge¬ 
ther. I cannot detect any traces of an operculum. The 
species is not unlike the form figured as a variety of S. sim¬ 
plex by Dr. Coughtrey in pi. xx. fig. 10, l. c. The hydro¬ 
thecas, however, are closer together and exhibit less numerous 
wrinkles in my specimen. 
Serlularella ramosa , sp. nov. (PI. XVI. figs. 5, 5 a.) 
Trophosome. Hydrorhiza consisting of short matted fibres. 
Hydrocaulus attaining a height of about 3 inches, strong and 
shrubby. Main stem flexuous, giving off alternate pinnas 
often themselves pinnate. Internodes short; joints oblique 
and conspicuous. Hydrothecas large, urceolate, somewhat 
tumid, smooth ; upper third divergent, one to each internode; 
orifice four-sided, with short rounded teetli at the angles. 
Colour brown. 
Gonosome. Gonangia long, ovate, smooth, with a distinct 
four-sided neck; orifice quadrangular, with four teeth. 
Locality. New Zealand {Dr. Jolliffe). 
This species, as regards the shape of the hydrothecas, has 
affinities with S. polyzonias, Linn., or still more with S. 
turgida , Trask (Proc. Calif. Acad., March 1857). I found a 
tiny scrap of the present form among zoophytes from Bass’s 
Straits {Dr. Harvey ) ; it may, however, have got mixed up 
with them accidentally. 
Sertularia, Linnmus (in part). 
The very numerous species of Sertularia seem to me to 
resolve themselves naturally into three groups, two only of 
which are represented among the following species. 
a. The first section is that whose type species may be taken 
as S.pumila —a very natural group characterized by the oppo¬ 
sitely-paired arrangement and tubular form of the hydrothecm, 
and by the possession of ovato-globular, usually smooth, go- 
