31) 
For subdividing this section other reasous may be found later, I feel unable with the material 
at hand, to make a proposal in that direction. 
Section Strzato-Balanus. This section contains species that have no pores in the 
the parietes and radii (which belonged to Darwin's Section F or might have been considered 
to belong to it). They show the common features of having the scutum striated longitu- 
dinally, and of having, as a rule, narrow radii. These species — 2. amaryllis Darwin, B. albus 
n. sp., &. dzmae n. sp., B. maculatus n. sp. — seem to form a very natural group. Several 
species belonging to it are of somewhat larger size. Whether B. Hamer? Ascanius is to be 
placed in this section or into the next is difficult to say: it has the scutum feebly striated 
longitudinally, but its radii are not so narrow as is the case in the more typical species. 
Balanus vestitus Darwin, 4. tmperator Darwin, and 2B. floscu/us Darwin have narrow radii also 
(they are even absent in 2. floscwlus) and might also be included in this section; they do 
not show, however, the characteristic feature of having the scutum striated. 
Section Sol¢do-Balanus. This section contains species which have the parietes, radii and 
scutum smooth, as a rule rather thick, the parietes and radii, moreover, without pores. They 
have also a solid basis, with crests running over the surface, or with narrow canals radiating 
from the circumference. The radii are rather broad and most of the species seem to be of small 
dimensions only. 4. soctatis Hoek, and &. maldivensis Borradaile belong to this section, which, 
embraces 4. auricoma n. sp., B. celiatus n. sp., and B. compressus n. sp., of the material 
collected by the “Siboga”’. 
Section JJemébrano-Balanus corresponds to Darwty’s Section E and contains the 
species with a membranous basis. I am in doubt whether this is really a good section, 
that is, a natural group of species: like Darwin himself I do not feel sure that the species 
really belong together. That the basis is membranous, or is non-calcareous, is a negative 
character only. But as only one species of the Siboga-material belongs to it, and is, more- 
over, a somewhat abnormal form, I had better not enter into discussion about this question. 
The new Siboga-species is 4. longirostrum, which is nearly related to B. declivis Darwin; 
it has non-porose parietes and lives embedded in sponges. Numerous segments of both 
rami of the fourth cirrus, are, in this species, armed with transverse groups of triangular 
teeth, such teeth occurring also, but smaller, on most of the segments of the 2™ and 
3" cirri. This shows, perhaps, that the species is allied to some of the species of the Section 
Armato-Lalanus. 
Section Armato-Lalanus. The species of this section have as a rule the parietes and 
radii without pores; some of its species, which were already known and which I propose 
to include in it, were considered by Darwin to belong to Section F. This section emerges 
into the genus Acasta’ by some of the segments of the anterior ramus of the 4" cirrus 
being armed with rows of teeth, and it is at the same time nearly related to the section 
1 Darwin has pointed out already that some of the species of his Section F (B. terebratus, B. allium, B. quadrivittatus) can 
hardly be separated naturally from the genus Acasfa. It is certainly very interesting that DARWIN’s main reason for separating them — 
viz. the structure of the 4th cirrus in Acasfa — has now been found not to exist: the structure of that cirrus in these species corresponds 
exactly with that of some species of Acaséa. 
31 
