The Zoologist — February, 1874. 3851 



the sand, a load of which at every thrusting operation is pushed away from 

 under the crab, and deposited outside the carapace. The four plates then 

 close, and are withdrawn closed, previously to beiug opened and charged 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 Liraulus 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 Hamburg contained thirty 

 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 beiug 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 in 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." 



Limulus has often caused rae to be undeservedly blamed, because 

 they so constantly hid themselves in sand by day in the perfectly 

 aerated water of the Hamburg and Crystal Palace aquaria, while in 

 the imperfectly aerated water of the aquaria of Hanover and Berlin 

 they climbed about the rocks all day, at their surface, and of 



