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 l stated that " the excretory opening [in Porcellanaster 

 cseruleus"] 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 pedicellarise in Baihybiaster described by Danielssen and Koren. 2 Whether 

 they actually perform the functions of pedicellarise or not, I 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 3 

 in 1882, seems to be a synonym 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 cseruleus, 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 rangee, comme chez les Ctenodiscus"). 

 I venture to think that on closer examination a double row (i.e., a supero-marginal 



1 Voyage of the Challenger, The Atlantic, London, 1877, p. 380. 



2 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 Oomptes rendus (Dec. 1882), t. xcv. p. 1379. 



