ióo 



Patella-Balanus: as we shall see, B. proripicns of that section has also small teeth on some 

 of the segments of the 4 th cirrus. Three of the new species collected by H. M. S. "Siboga" 

 are placed in this section : B. arcuatus, B. quinquevittatus, and B. hystrix. The last named 

 has the parietes permeated by pores ; therefore by this species this section passes into the 

 Section Ort/io-Ba/antis, which, as it is here proposed, would correspond with Darwin's 

 Sections C and D. 



Section Patclla-Balantcs. This section corresponds with Darwin's Section B. It is repre- 

 sented in the Siboga-material by five species, two of which were knovvn to Darwin (B. cal- 

 ceolus Ellis, and B. navicula Darwin). The remaining three (B. cornnhis, B. investitits, and 

 B. proripicns) 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-Ba/anus, 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-Balanns. It is for a single, yet well-defmed species, that I feel obliged 

 to create this section, namely B. pentacrini 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 Hexclasma : it can be considered as forming the 

 transition from the genus Balanus 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 

 beein his task before he has succeeded in brinoine tosether 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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