5U THE VOYAGE OF H.M.S. CHALLENGER. 
of those of Errina labiata (Pl. IV.), in order to accommodate their length within the 
ampullee. 
The male stocks of Pliobothrus symmetricus are in every way similar in structure to 
the female, with the exception that they bear male gonophores instead of female in their 
smaller ampullie. 
The male gonophores (Pl. VII. fig. 3) are sacs containmg a number of small ovoid 
bodies which contain spermatozoa or sperm-cells in various stages of development. The 
exact structure of these smaller bodies, and their relations to the endoderm, were not 
determined. 
Errina, Gray. 
The genus Lrvina was formed by Gray to contain the Millepora aspera of Linneeus 
and Esper. Gray gave a short diagnosis of the genus in the Proc. Zool. Soc., 1835, p. 85, 
from specimens in the British Museum; and this was supplemented by Saville Kent, 
in a paper published in the same journal for 1871 (p. 282) by further reference to the 
same specimens. A specimen dredged by H.M.S. Challenger off the mouth of the Rio 
de la Plata, in 600 fathoms, is clearly referable to this genus, but represents a new species 
for which the name Errina labiata is adopted. 
Ceenosteum of Hrrina labiata (PI. I. fig. 7). 
The ccenosteum occurs in the form of arbuscular multi-ramified masses, which have an 
extreme height, in the specimens obtained, of about 5 inches. The mass of branches 
and branchlets has a tendency to form an irregular flabellate expansion, which in the 
largest specimen obtained has a breadth of about 4 inches. The main stems, which 
are irregularly oval in section, being flattened in the plane of the flabellate expansion, 
have a longer diameter of about two-thirds of an inch. They, as well as the remainder 
of the ccenosteum, are composed of a compact, hard, glistening, white, calcareous tissue. 
At their bases, this tissue spreads over and encrusts objects to which the coral mass is 
adherent. In one specimen obtained, the support thus fastened on is a large dead mass 
of Sporadopora dichotoma. ‘The main stems have a surface which appears smooth and 
even to the naked eye, but when magnified is seen to be scored in all directions 
by small more or less tortuous canals, which in the recent state contain the superficial 
ramifications of the coenosarcal meshwork. In specimens in which certain regions of the 
main stems are dead and somewhat corroded, these scorings of the surface are much 
more conspicuous than on the recently living regions, and give the surface a roughly 
engraved appearance. The finer branches have a tendency to develop mostly on one 
face only of the flabellate expansion, one face of the main stem being frequently devoid of 
