108 Mr. D’Arcy W. Thompson on neiv Hydroid 
network. Hydrocaulus attaining a height of 4 or 5 inches, and 
giving off at close intervals alternate pinnas, which, towards 
the upper part of the hydrocaulus, are themselves pinnate. 
Joints, on stem, just below the points of origin of the pinnae ; 
on pinnae, between each pair of hydrothecae. Hydrothecae in 
pairs, subalternate, tubular, smooth, diverging for about half 
their length ; orifice furnished with six long pointed teeth. 
Gonosome. Gonangia springing from a point just below the 
base of a hydrotheca, large, elongate, inversely conical, trun¬ 
cate, smooth, with two long teeth or spines on opposite sides 
of the orifice ; aperture slightly marginate, minutely dentate. 
Localities. George Town, Bass’s Straits, &c. {Dr. Harvey) • 
Cape Wilson, Port Philip, &c. {Dr. Ferd. Muller). [New 
Zealand ( Gray , Hutton , and Coughtrey ).] 
The figure of this species, though somewhat rough, and 
the description, though, as usual, short, which are given by 
Lamouroux in his 1 Polypiers flexibles,’ are amply sufficient 
to determine his specimens as coinciding with the Sertularia 
abietinoides of later authors. 
One of the specimens sent home by Dr. Ferd. Muller is 
marked, in his handwriting, u Sertulariapennigera, Lamarck.” 
I am unable to find any reference to such a species; but S. 
millefolium , Lamarck, appears to coincide very closely with 
the present form. 
The species appears to be a very abundant one, and, at the 
same time, shows a very considerable tendency to variation. 
In colour my specimens range from a dark brown or black 
to an indescribable greenish hue, which Lamouroux seems to 
have tried to render by “ vert-rougeatre foncd.” The latter 
variety seems altogether more lax and delicate; the hydro¬ 
thecas are longer and more divergent, the pinna} longer, the 
whole hydrocaulus more graceful and feathery. The gonangia 
also, which in the ordinary form are restricted to the main 
stem, in this one occur also on the pinnae, though apparently 
never more than a single one to each. 
This zoophyte forms dense and luxuriant masses, over¬ 
growing shells, the stems of Fuci , &c. &c. The teeth upon 
the margins of the hydrothecae are often so long and sharp 
that Lamouroux described them as cilia { ll marginibus cilia- 
tis”). As a general rule the two teeth on the side nearest 
the stem or pinna are separated by a wider interval than 
occurs between the rest. 
Sertularia pulchella, sp. nov. (PI. XVIII. figs. 3, 3 a.) 
Sertularia biouspida (?), Lamarck, Hist. Nat. des Anim. sans Vert, 
vol. ii. p. 121. 
Tropbosome. Hydrorhiza consisting of a long slender fila- 
