14 



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 of a tank (which in 

 Hamburgh contained tliirty inches of water in depth perpendicularly), 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 Limidits 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 

 longitudinal or vertical, or at some combination of the two ; and the crab then turns 

 over." 



The masillipeds, no doubt, aid 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 Lwnulus 

 polyphemus as observed by the Eev. S. Lockwood, Ph.D., in its native haunts (Rariton 

 Bay, New Jersey, U. S.). 



" The King-crab delights ia 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 fulcrum 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 excavating action ; for the alternate 

 doubling up or inflecting and straightening out of the two carapaces, with the pushing- 

 purchase exerted by the tail, accomplish both digging and subterranean progression. 

 Hence the King-crab is worthy to be called the ' Marine Mole '" *. 



» ' The American Naturalist,' 8vo, vol. iv. 1870, p. 257. 



