54 
THE VOYAGE OF H.M.S. CHALLENGER. 
having the ramuli all directed towards one and the same side, so as to give to the colony 
a front and a back aspect. In the hydrothecse also a similar unilateral direction is 
apparent, for those of opposite sides, instead of lying as usual in a single plane, are 
directed obliquely towards one side of the stem, and thus lie in two planes which 
converge towards its axis. 
Sertularia clausa , n. sp. (PI. XXV. figs. 3, 3a). 
Trophosome. — Stem slender, transparent, irregularly branched, internodes carrying 
each a single hydrotheca. Hydrothecse alternate, distant, conical, slightly tumid below, 
adnate to the internode for about half their height, then diverging ; orifice subquadrate, 
covered by a pyramidal lid which is composed of four triangular valves. 
Gonosome not present. 
Locality. — Station 320, off Monte Video; lat. 37° 17' S., long. 53° 52' W. ; depth, 
600 fathoms; bottom, green sand; bottom temperature, 37°'2. 
Sertularia clausa is a small, much-branched, slender form, with a thin very trans- 
parent perisarc. The branches are given off at a wide angle, each from a point just 
below the base of a hydrotheca, and are irregular in their disposition and direction. 
The hydrothecse are separated from one another by rather wide intervals. From a some- 
what wide base they become gradually narrower towards the orifice, which is obscurely 
quadrate. As in many other species, the orifice is provided with a membranous four- 
valved operculum, but instead of this being filmy and perishable as in most of the species 
which possess it, it has here considerable firmness and forms a well-developed, permanent, 
pyramidal lid. This is composed of four triangular valves, which when in apposition form 
the four sides of a pyramid. 
The delicacy and transparency of the periderm is probably connected with the very 
considerable depth of 600 fathoms from which the species was dredged. 
Sertularia implexa, n. sp. (PI. XXVI. figs. 1, la). 
Trophosome . — Stem profusely and irregularly branched ; branches slender, given off in 
all directions, and forming loosely entangled masses. Hydrothecse alternate, rather distant, 
deep, adnate to the internode for somewhat less than half their height, apocauline side 
nearly plane, epicauline side ventricose, orifice with the margin divided into four teeth 
and provided with four delicate membranous valves. 
Gonosome not present. 
Locality . — Station 314, between Cape Virgins and the Falkland Islands ; lat. 51° 35' S., 
long. 65° 39' W.; depth, 70 fathoms. 
