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 Chtliamalinac 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 110 means so doubtful. For 

 the present, for practical reasons only, it may remain, like Acasta, 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 : Hexelasma corolliforme Hoek was dredged by the Challenger near 

 Kerguelen (at a depth of 270 m.) and was collected again by ' Doflein (fide Krüger 1 ) in 

 the Bay of Sagami near Misaki ; H. hirsutum Hoek was dredged by the Triton in the Faroe 

 Channel (at a depth of 930 m.); H. callistoderma Pilsbry was collected in Japan waters (at 

 a depth of 140 m.) and H. hoekianum Pilsbry in Behring-Sea (at a depth of 77.5 m.). The 

 new species H. velutinum and H. arafnrae come from the Malay Archipelago where they 

 were found at depths varying from 204 — 560 m, 



1. Hexelasma velutinum n. sp. PI. 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 less 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 (PI. XXVI, fig. 3 and 4), that from Station 105, however, being 

 more cylindrical (PI. XXVI, 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 Krüger, Paul, Beitrage zur Cirripedienfauna Ostasiens. Abhandl. dei- Math. phys. Klasse der K. Bayer. Akad. d. Wissensch. 

 II Suppl. Bd. 6. Abhandl. 191 1. p. 55. 



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