SOLEN. 153 
there are about fifteen, and in the upper, thirty of different 
sizes. The foot is long, strong, muscular, and subcylindrical, 
fixed to the comparatively small body about the middle of the 
shell; it has the power of changing the terminal portion mto 
all shapes, from the fine elongated tentacular point, to the 
decided club-shaped extremity ; the foot, when half-extended, 
is oblique, and obtusely pomted; the colour is pale yellow- 
white, marked for some distance anteally with exceedingly 
fine, very pale, close, lead-coloured lines. 
The animal has two systems of locomotion; the one for 
ascending from its deep perpendicular hole, the other for 
changing its locality, which it can effect by darting forward 
with a rapidity equal to that of the Pectines. The foot has a 
decided tubular aquiferous canal, from its junction with the 
body to within a short distance from the termination; the 
outer tissue appears homogencous, but the entire conical cavity 
is furnished with strong elastic fibres, which doubtless have 
the power to close or greatly contract it. How the water 
gets access to the cavity is doubtful; I could detect no orifice 
either at the point or junction with the body; one must 
suppose it to enter by the mouth, stomach, and walls of the 
crystalline stylet, and, from thence, to have a contact with the 
enveloping membrane of the viscera, if not an inward com- 
munication. What is the particular ceconomy of this sort of 
foot, which is im some measure analogous to that of the 
Lucine, only im them it is perforated throughout, is at pre- 
sent hypothetical. Can it be, in Solen, to give it increased 
power and elasticity, and in its deep hole of two feet or 
more, by a sudden compression to aid the muscular extension, 
which alone could not effect the ascent of the animal from its 
deep lodgement ? and is the compressive action also the agent 
to enable it, when out of its retreat, to dart with such unusual 
rapidity ? 
There are on each side a pair of equal-sized, long, linear, 
narrow branchize, which, after getting rid of the interposition 
of the body, proceed, fixed to the roof of the long dorsal range 
of the mantle, to the branchial siphon, each pair united to 
the other, to deposit m it their attenuated poimts, as in the 
