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Patella-Balanus: as we shall see, B. froripiens of that section has also small teeth on some 
of the segments of the 4 cirrus. Three of the new species collected by H. M. S. “Siboga”’ 
are placed in this section: B. arcuatus, B. guinguevittatus, and B. hystrix. The last named 
has the parietes permeated by pores; therefore by this species this section passes into the 
Section Ortho-Balanus, which, as it is here proposed, would correspond with Darwin's 
Sections C and D. 
Section Patella-Balanus. This section corresponds with Darwty’s Section B. It is repre- 
sented in the Siboga-material by five species, two of which were known to Darwin (B. cad- 
ceolus Ellis, and &. xavicula Darwin). The remaining three (4. cornutus, B. investitus, and 
B. proripiens) are new. The elongated shell and the boat-shaped basis form the main features 
to recognize the species of this section and which no doubt constitutes a very natural group. 
This section is-nearly related to the foregoing section Armato-Balanus, in different respects, 
as also by the circumstance that some species have small teeth along the inner face of some 
of the segments of the third cirrus. In one of the species (B. proripiens) these are also 
observed on some of the segments of the fourth cirrus. 
Section Bathy-Balanus. \t is for a single, yet well-defined species, that I feel obliged 
to create this section, namely £&. fentacrini n. sp. from 200 to 300 m. It has the parietes, 
radii, and basis without pores and therefore would belong to Darwin's Section F, but, I 
think, it should form a section by itself, since it has the labrum without a notch, a small and 
shallow excavation indicating the place the notch occupies in the other species. Having well- 
developed radii and a calcareous basis, there is no reason to doubt its belonging to the genus 
Balanus. On the other hand it cannot be denied that it corresponds in the structure of its 
labrum to the species of my new genus /Yexe/asma: it can be considered as forming the 
transition from the genus Lalanus to that of Hexelasma. 
As will be easily understood, the classification here proposed aims only at bringing 
together in natural groups those forms or species which I think really belong together. It is 
not my opinion that the arrangement is a final one, and it is only with great reserve that I 
venture to propose putting it in the place of Darwin’s classification of 1854. And especially 
so, since I am not entirely satisfied that it will be possible to include all the species known at 
present, in the sections or divisions as they are here proposed. Yet Darwin’s sections must 
be revised in certain respects, and the sections added to the genus by later authors cannot be 
accepted. Several of the new species described since the publication of Darwin’s Monograph 
claim a place in the system, although they do not enter so well into one of the old sections. 
Therefore an attempt to improve the classification was I think fairly justified. If the one here 
proposed does not prove to be a good one, it need not be maintained — it may, however, turn 
out to be of use, at least in some respects, to a future monographer of the genus. The genus 
certainly needs to be thoroughly dealt with by a good specialist! He should, however, not 
begin his task before he has succeeded in bringing together sufficiently rich material of the 
existing species, and that in a good state of preservation — and he must not expect that 
his task will be a light one. 
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