246 
pondence, so far as the animal’s body is concerned, is not complete, in consequence; as 
Hexelasma has the rostrum without alae, and as the Chthamalinae have the rostrum with 
alae, while it has radii rule in the Balaninae, the question of the position of this new genus 
is decidedly interesting. I feel unable, however, to settle it in a satisfactory way with the 
material at my disposal — perhaps younger stages of the shell of Hexelasma would go far 
to show, that its relation to one of those Sub-families was by no means so doubtful. For 
the present, for practical reasons only, it may remain, like Acasfa, in the neighbourhood 
of the genus Balanus, the two genera certainly showing in several respects superficial cor- 
respondence. 
This is again one of these difficult points, which the zoologist working up the material 
belonging to a certain group and brought home by a scientific expedition may discuss, but 
which can be settled only by monographical study of the whole group, and with the aid of the 
whole material of the group at present available. The task of a reporter, as is my case, is to 
give good descriptions and accurate figures: for more theoretical considerations the material 
handed over to him, although rich as in the case of the Siboga-Cirripedia, is obviously far 
too incomplete. 
To judge from the six species that are at present known, the new genus has a 
world-wide distribution: AHexelasma corolliforme Hoek was dredged by the Challenger near 
Kerguelen (at a depth of 270 m.) and was collected again by Dorvetn (fide Krtcer*) in 
the Bay of Sagami near Misaki; 7. hzvsutum Hoek was dredged by the Triton in the Faroe 
Channel (at a depth of 930 m.); AH. callistoderma Pilsbry was collected in Japan waters (at 
a depth of 140 m.) and “4. hoektanum Pilsbry in Behring-Sea (at a depth of 77.5 m.). The 
new species /7. velutinum and H. arafurae come from the Malay Archipelago where they 
were found at depths varying from 204—560 m. 
1. Hexelasma velutinum n. sp. Pl. XXVI, fig. 1—16. 
Shell white, covered by a thin velvety epidermis. Alae triangular, with their summits 
obliquely rounded off. Orifice large, pentagonal. Inner surface of scutum and tergum white. 
Scutum with two longitudinal furrows, one of which is jess distinct than the other; adductor 
ridge and cavity for adductor muscle hardly visible. Tergum only very indistinctly beaked and 
with the extremity of the spur truncated. 
H. M.S. “Siboga” collected this species at three different Stations; unfortunately, at each 
station a single specimen, or one and an incomplete specimen only were dredged. The specimens 
from the different stations differ from one another in appearance: those from Station 59 and 
201 being of a conical shape (Pl. XXVI, fig. 3 and 4), that from Station 105, however, being 
more cylindrical (Pl. X XVI, fig. 1), with the circumference at the basis hardly larger than at 
the orifice. The latter specimen is, however, unsymmetrical, the shell being considerably higher 
at the one than at the other side. Although there is also a small difference in the shape of 
1 KrUGER, PaAuL, Beitrige zur Cirripedienfauna Ostasiens. Abhandl. der Math. phys. Klasse der K. Bayer. Akad. d. Wissensch. 
II Suppl. Bd. 6. Abhandl. 1911. p. 55. 
rs 
