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which have the radii narrow or absent (B. flosculus) or not developed at all (4. vestetus), and 
that Darwin's section C contains also B. perforatus, which has the radii either not at all 
developed, or extremely, or only moderately narrow. GrRuveEL's species might perhaps find a 
place in the latter section, which contains those species of Ba/anus which have the parietes and 
the basis permeated by pores, and the radii, if developed, not permeated. 
Returning to the species represented in the collection brought home by H. M. S. 
“Siboga’’, I will not enter too much into details regarding my experience (and very great diffi- 
culties) in dividing the new species into the different sections of the genus. In several instances 
this was found to be quite impossible. But to go on as was done hitherto, and to create a 
new section for every species that did not enter so well into one of the sections previously 
proposed, seemed also unsatisfactory. The conclusion was that I adopted a somewhat new 
classification of the species of this genus, but without departing more than necessary from the 
original division as proposed by Darwin. I think this classification must speak for itself. I 
only wish to add that as I was obliged to include some of the known species in other sections, 
and as the limits of these sections had to undergo some changes in consequence,.and a few 
other sections were to be introduced and a few of the old ones to be cancelled, I have thought 
it better, to avoid confusion, to designate these sections in future with special names, as | 
did with those of the genus Sca/pe//um, instead of using the characters A, B, C, etc. as was 
done by Darwin. 
The sections I wish to propose are the following: 
Section MM/ega-Balanus (corresponding with Darwin's section A) is so-called, because 
it contains the largest forms of existing Balani. This section is represented in the Siboga- 
material by one well-known species only, so I have nothing to remark with regard to it. 
Section Ovrtho-Lalanus is a combination of Darwin’s Sections C and D; it contains 
Balani having the parietes permeated by pores, the basis sometimes permeated and sometimes 
not permeated, and the radii not permeated. Numerous species (DARwin knew 14 living species) 
belong to this Section, which, however, in the Siboga collection is represented by few species 
only: 4. amphitrite Darwin in different varieties, B. alatus n. sp. from a depth of over 500 m., 
and £&. minutus from 80 m. To this section belongs &. trzgonus Darwin, the third cirrus of 
which, according to KricGerr, is furnished with curious thorns (“merkwiirdige Dornen’’) along 
the anterior face’) of the segments. These curved hook-like teeth, as Darwin called them and 
which he thought were peculiar to Acasfa, are present also on the third cirrus of B. amphi- 
trite, B. alatus, and B. minutus. None of the species of Darwin’s Section D are found in the 
Siboga-collection. I venture to propose to include it with Section C in my Section Ortho-Lalanus, 
being of the opinion that the porosity or non-porosity of the basis is not of sufficient impor- 
tance for separating these two sections. As Darwin pointed out himself, some species of Section 
C (B. improvisus, B. nubilus of the living species) have the basis imperfectly porose, whereas 
a species of Section D (4. fatellaris) has the basis “sometimes permeated by imperfect pores’’. 
1 KriGEer also compares them — and of course he is right there — with the spines observed in Acasfa: I do not quite 
understand, however, how he can say that they are found on the dorsal side (,auf der Riickseite’”) of the segments. They are in all the 
species on the inner, anterior face of the segments. 
