Hexelasma and i to Balanus. The latter genus seems to occur only exceptionally so far down 

 as 564 m. (B. a/a fits n. sp.) and can safely be considered a true shallow-water genus. 

 Hexelasma, which is nearly related to Balanus, represents the deep-water form of that species ; 

 Poecilasma, Alepas and Dichelaspis are shallow-water genera, some species of which occur 

 at considerable depths. This is, after all, also the case with the genera Verruca and Scal- 

 pellum, the difference being that the number of deep-sea species of these latter genera is 

 much more considerable, and, in the second place, that they occur at much greater depths. 

 In both respects Scalpellum still greatly surpasses Verruca : when we descend,' in the Malay 

 Archipelago, to depths of more than 1300 m., the only species of Cirripedia we meet with 

 belong to the genus Scalpellum. The Cirripedia of the Challenger-expedition showed the same 

 peculiarity, although a species of Verruca was still collected at a depth of 3400 m., Scalpellum 

 was the only genus occurring at still greater depths, from 3600 — 5000 m. 



On the other hand, we must not forget that these genera, Scalpellum and Verruca, 

 although inhabiting great depths, are represented also in shallow water, and are found even 

 on the shore in single species {Sc. Peroni (Gray), Verruca strómia (Muller)). We may therefore 

 conclude that these genera occur at any depth, but that the number of species increases it 

 we proceed from less deep into deeper parts of the sea, while the other genera either have 

 no species at all in deeper water (Pollicipes, Pyrgoma, Tetraclita etc), or, although showing 

 the greatest distribution in shallow water, are represented also in much deeper water {Alepas, 

 Dichelaspis, Poecilasma, Balanus etc.) with a few or a single species. In this respect the 

 genera Megalasma and Hexelasma seem to occupy a special position : though they have not 

 been observed at very great depths, say of more than 1000 m., all the species we know are 

 found in deeper water, ranging from about 100 to 900 m. So when it comes to the point 

 they would be the only true deep-sea genera of Cirripedes at present known. 



With few exceptions, the deep-sea species were met with only once : the greater the 

 depth, the more seldom is a species collected that was already found at another station. Most 

 of these deep-sea species are, moreover, represented only by a single or few specimens. This 

 is partly explained by the way in which the material from the bottom of the sea is collected, 

 and may be partly due to the fact, that these species live somewhat isolated, not forming- 

 dense aggregations as do commonly the floating species of Lcpas and the shallow-water-species 

 of Balanus and other genera. But, perhaps, our opinion on this point would be different if we 

 could investigate the depths of the ocean in the same way as we can explore a meadow, 

 counting if we like the specimens of wild plants occurring there. When discussing the geographical 

 distribution of the Cirripedia of the Malay Archipelago we will have to return to this subject. 

 With regard to the true deep-sea species of Scalpellum, it may here be pointed out that the 

 size of the Siboga-specimens was by no means so remarkable as was the case with the species 

 collected by the Challenger. The latter could truly be said to show that the conditions of life 

 in the deep-sea by no means exercised a dwarfmg effect upon these animals, for they contain 

 the largest forms of pedunculate Cirripedia observed. On the contrary, the species of Scalpellum 

 from the greatest depths collected by H. M. S. "Siboga", are all of medium size or even small 

 species. The only really large form of Scalpellum represented is Sc. Steamsi, and this has a 



