x 
Hexelasma and 1 to Balanus. The latter genus seems to occur only exceptionally so far down 
as 564 m. (2. alatus n. sp.) and can safely be considered a true shallow-water genus. 
Flexelasma, which is nearly related to Lalanus, 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- 
fellum, 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 Scalfel/um 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 BOD , 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, Scalpel/um and Verruca, 
although inhabiting great depths, are. represented also in shallow water, and are found even 
on the shore in single species (Sc. Peronz (Gray), Verruca strémia (Miiller)). 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 (4/efas, 
Dichelaspis, Poecilasma, Balanus etc.) with a few or a single species. In this respect the 
genera JJegalasma 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 Zefas and the shallow-water-species 
of Lalanus 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 Scalpel/um, 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 dwarfing 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. Stearns¢, and this has a 
