6 
THE VOYAGE OF H.M.S. CHALLENGER. 
from the sides of which equidistant, opposite pinnae, also composed of geminate zocecia, 
are given off at right angles. Zocecia geminate, closely connate, subcompressed, the 
oral portion subtubular and twisted round to opposite faces, front and back, in each 
pair. Surface smooth, entire, with a row of four to six puncta on each side, and a few 
on the front. Peristome slightly thickened. 
Habitat . — Station 122, lat. 9° 5' -l O' S., long. 34° 49'-53' W., 32 to 400 fathoms, 
red mud. Station 24, off Culebra Island, 390 fathoms, Pteropod ooze. Station 23, off 
Sombrero Island, 450 fathoms, Pteropod ooze. Off Barra Grande, Brazil, 400 fathoms. 
[Gulf of Florida, 120 to 127 fathoms, Pourtales.] 
v 
This very remarkable form affords a striking example of dimorphism. Though well 
described in most respects by Prof. Smitt, in both its forms, that excellent observer does 
not appear to have noticed the precise way in which the two are connected. “The 
species,” he says, “ in its erect state, from its ivory-white aspect and delicate stem, to 
the naked eye much resembles a Crisia. But closer examination shows the zocecia 
to be arranged much as they are in Gemellaria, back to back in pairs, and apparently 
spirally arranged round an imaginary axis, owing to the circumstance that the zocecia 
in the same longitudinal series have their mouths turned alternately to right and left.” 
The stem and branches, as observed by Prof. Smitt, are articulated or divided into 
internodes, which in the stem consist of two or three pairs of zocecia, from the 
lower pair of which alone the lateral branches arise, exactly opposite to each other ; 
each branch springing from one of the two zooecia. 
Prof. Smitt does not appear to have met with specimens showing the mode in which 
the erect portion originates, and his description of the adnate zooecia, and of the 
stoloniform tubes on which they are formed, does not convey exactly the true nature 
of the latter. In the specimen of Pasythea eburnea procured off Sombrero Island, the 
mode of origin and the nature of the connection between the adnate and erect portions 
are beautifully displayed. 
On a small fragment of Coral or Myriozoum, four or five very young growths are 
seated, each of which arises from the centre of a circular, somewhat tumid disc, which 
is hollow, with thin, transparent, slightly calcified walls. The first internode of the erect 
stem consists of a double connate tube. The subsequent internodes are developed, each 
into two or three pairs of zooecia, the lowermost one or two being more or less abnormally 
formed. From the outer border of this radical disc proceed four or five very slender and 
delicate, adnate stoloniform jointed tubes, upon which at rare intervals a decumbent 
Hippothoiform zocecium, of the same size and form, as those in the erect part of the 
growth, is developed ; whilst the tube itself connects one central disc with another. The 
occurrence of zooecia in the course of the stoloniform tubes gives the growth very much 
the aspect, as Prof. Smitt remarks, of a dwarf Hippothoa divaricata, 
