852 
THE VOYAGE OF H.M.S. CHALLENGER. 
“The species have been distributed among thirteen genera, of which only one is new 
to science. This is the genus Megalasma ; the only species which represents it has a 
very characteristic shape, though it is doubtless nearly related to the genus Pcecilasma, 
Darwin, and belongs with the latter genus to that group of pedunculated Cirripedia which 
contains also the genera Diehelaspis and Lepas. In all these genera the capitulum has 
the same number of valves (five), the structure of the body being also much the same, 
and showing only secondary differences. Whereas, however, the species of Lepas live 
only at the surface, those of the nearly . related genera were taken at various and some- 
times considerable depths. One of the species of Diehelaspis ranges even as far down as 
1000 fathoms. The surface animals as well as those attached to rocks and stones within 
Fig. 317 . — Megalasma striatum, Hoek. Station 204, off the Philippines, 100 and 115 fathoms. 
the tide marks live as a rule in numerous assemblies close to one another ; in the deep 
sea, however, the Cirripedia seem to live rather solitarily. And this assertion must not 
be considered hazardous, for, though the contents of the dredge or trawl do not 
necessarily show the exact number of specimens living together at one spot, one naturally 
arrives at the conclusion, as it was found that by far the greater part of the deep-sea 
species are represented by single or very few specimens only. 
“ The genera Conchoderma and Alepas represent a second family of pedunculated 
Cirripedia. In this family the capitulum shows rudimentary valves only, or sometimes 
even no valves at all. In the Challenger collection the genus Conchoderma is represented 
by well-known species which live at the surface ; of Alepas , on the other hand, there 
