INTRODUCTION. 9 
On the Names given to the different parts of Cirripedes. 
In my former volume I stated that I had found it indispensable, in part owing to 
the extreme confusion of the nomenclature previously used, to attach new names to several 
of the external parts of Cirripedes. Almost all these names are applicable to the Balanide, 
or Sessile Cirripedes, and to the Verrucide ; but a few additional names are requisite, 
which, together with the old names, will, I hope, be rendered clear by the accompanying 
woodcuts. In Sessile Cirripedes, the whole of that which is externally visible, may, for 
convenience sake, be divided into the operculum or opercular valves (valve operculares): 
and the shell (testa), though these parts homologically present no real difference. ‘The 
operculum is seated generally some little way down within the orifice of the shell; but in 
very young specimens, and in Verruca, the operculum is attached to the summit of the 
shell, and in these cases the shell, without the operculum be removed, can hardly be said 
to have any orifice ; though, of course, the opercular valves themselves have an aperture 
for the protrusion of the cirri. 
The shell consists of the daszs (called the support by some authors), and of the com- 
partments (teste valve), which in recent specimens vary from eight to four in number, and 
occasionally are all calcified together. 
The compartment, at that end of the shell (fig. 1) where the cirri are exserted through the 
aperture or lips of the operculum, is called the carina (fig. 4) ; the compartment opposite to 
it, is the rostrum (in all fossil specimens, like fig. 2),—these two lying at the ends of the 
longitudinal axis of the shell. Those on the sides are the dateral compartments; that 
nearest the carina, being the carino-lateral (fig. 3) (teste valva carino-lateralis), that 
nearest the rostrum, the rostro-/ateral, and middle one simply the /ateral compartment 
(fig 3): but these three compartments are rarely present together. The rostro-lateral com- 
partment, which always resembles fig. 2, and may be always known by having radii on 
both sides, is not known to occur in any fossil species; and hence we are here only con- 
cerned with the lateral and carino-lateral compartments. The compartments are separated 
from each other by sutures, which are often so fine and close as to be distinguished with 
difficulty. The edge of a compartment, which can only be seen when disarticulated from 
its neighbour, I have called the sutural edge (acies suturalis). 
Each separate compartment consists of a wall (paries), or parietal portion (pp in figs. 1 
and 4), which always grows downwards, and forms the basal margin; and is furnished on 
the two sides either with ale (fig. 4), or with radii (fig. 2), or with an ala on one side and 
a radius (fig. 3) on the other. 
The radius (adopting the name used by Bruguiére, Lamarck, and others) differs 
remarkably in appearance (though not in essence) from the wall or parietal portion, owing 
to the direction of the lines of growth and the state of its usually depressed surface. In 
the upper part, the radii overlie the alz of the adjoining compartments: in outline 
2 
