130 THE VOYAGE OF H.M.S. CHALLENGER. 
entertained similar doubts as to the anal function of an excentral aperture on the 
abactinal area in Brisinga. In the case of Brisinga, however, the opening seems to 
me to be really an anal pore.) 
I have also found a similar pore at the extremity of the epiproctal peak in Ctenodiscus, 
and likewise in Hyphalaster. 
Sir Wyville Thomson! stated that “the excretory opening [in Porcellanaster 
cxruleus | is very distinct in the centre of the dorsal perisom of the disk.” This seems 
‘to me rather an inadvertent remark, and probably arose from the examination of a speci- 
men in which the extremity of the epiproctal funnel was either invaginated or actually 
broken off. 
I have observed under the microscope that some of the small membrane-invested 
spinelets on the abactinal area are either cleft or double, and simulate the appearance of 
the sacculate pedicellariz in Bathybiaster described by Danielssen and Koren.? Whether 
they actually perform the functions of pedicellarize or not, | am unable to say. They 
are generally situated near the marginal plates, and are usually most numerous in the 
neighbourhood of the madreporiform body. 
So far as I can judge from the description, the genus Caulaster, founded by Perrier * 
in 1882, seems to be asynonym of Porcellanaster. The new genus was established for 
the reception of two small starfishes dredged by the “ Travailleur” in 1880 off the north 
coast of Spain from a depth of 1960 and 2650 metres respectively, and the name 
had reference to the “dorsal peduncle ” with which they are furnished. Both specimens 
are very small, the larger of the two measuring only 5 mm. from the centre of the 
disk to the extremity of a ray. In the smaller one the embryonic plating of the 
disk is still present. The few striking characters briefly mentioned by M. Perrier 
accord in every particular with Porcellanaster; and so far as I am able to judge 
from the meagre information, I am constrained to regard these interesting starfishes 
as young forms of some species of that genus. As to their identity with, or dis- 
tinction from, the western Atlantic species Porcellanaster cxruleus, Wyville Thomson, 
I am not in a position to express an opinion. The smallest examples of that form 
with which I am acquainted are larger than those named Caulaster pedunculatus by 
M. Perrier. 
In referring to the alliance of his type with Ctenodiscus, M. Perrier states 
that the marginal plates of Caulaster form only a single row (“les plaques mar- 
ginales, peu visibles, ne forment qu'une seule rangée, comme chez les Ctenodiscus”). 
I venture to think that on closer examination a double row (7.e., a supero-marginal 
1 Voyage of the Challenger, The Atlantic, London, 1877, p. 380. 
* Nyt Mag. f. Naturvidensk., 1877, Bd. xxiii, 3die Hefte, p. 63; Den Norske Nordhavs-Expedition, 
1876-78, xi., Zoologi, Asteroidea, Christiania, 1884, p. 90. 
3 Comptes rendus (Dec. 1882), t. xcv. p. 1379. | 
