472 PROF. OWEN ON THE ANATOMY 
opened and charged with another load of sand ; and at the deposit of every load the whole 
animal sinks deeper into its bed, till it is hidden all except the eyes. The great hiding- 
shield of a carapace again prevents one from seeing whether this excavating work is aided 
by the fanning motion of the abdominal false feet, as is the case with the British Lobster ; 
but I think there is such fanning, as I have seen signs of sand being driven through the 
sand-orifices as if urged by a current of water. 
“The tail-spine of Limulus is used in locomotion in the following manner :— The animal 
having climbed up a rock in the Aquarium till it has got near to the top ofa tank (which in 
Hamburgh contained thirty inches of water in depth perpendiculalry), and having assumed 
a vertical position, leaves go its hold on the rock, and allows itself to fall backwards ; but 
its downfall is instantly checked, and the creature propelled upwards by a downward 
flap of all the strong overlapping false feet; and when the impetus given by them has 
ceased, the animal sinks down, but is prevented from falling prone on the floor of the 
tank by alighting on the tip of the perpendicularly hanging-down spine. The moment 
that is done, and before the creature has lost its balance on the spine, the false feet make 
another flap, and give another impulse upwards and forwards; and so it progresses by a 
combination of swimming and hopping, or by a succession of slow hops on one leg, as it 
were; and all this time the position of the carapace is. slanting, the top of the carapace 
inclining downwards at an angle of about 45°, the second segment of the body being 
at another inclination, and the tail-spine hanging freely vertically, as before mentioned ; 
and by being brought down by its joint at various deviations from the upright one, the 
spine changes the direction of the march, while the false (swimming) feet effect the actual 
propulsion. 
“The Limulus was fond of thus going about at night (generally remaining on the 
sand all day). Another use was made of the tail-spine, as a lever by means of which it 
righted itself when it fell off a rock on its back. The spine is then bent; i. e. its 
point is planted in the sand so that it makes an acute angle with the carapace, which is 
then so far raised that some of the feet are enabled to grasp a projecting surface, either 
iuc pape or vertical, or at some combination of the two; and the crab then turns 
over.’ 
The maxillipeds, no doubt, sidi in burrowing, as observed by Mr. Lloyd; but the chief 
fossorial agent, as indicated by the size and disposition of the principal muscular masses, 
is the cephaletral digging-shield. 
The operation of this is described in the subjoined note on the locomotion of Limulus 
polyphemus as observed by the Rev. S. Lockwood, Ph. D., in its native haunts (Rariton 
Bay, New Jersey, U. S.). 
“The King-crab delights in moderately deep water, say from two to six fathoms. It 
is emphatically a burrowing animal, living literally in the mud, into which it scoops or 
gouges its way with great facility. In the burrowing operation the forward edge of the 
anterior shield is pressed downward and shoved forward, the two shields being inflected, 
and the sharp point of the tail presenting the fulerum as it pierces the mud, while under- 
neath the feet are incessantly active, scratching up and pushing out the earth on both 
sides. "There is a singular economy of force in this excaváting action; for the alternate 
