ORDER XYPHOSURA ; LIMULUS OR KING-CRAB. 265 



covered by another shield of a somewhat hexagonal shape, 

 bears on its under surface five pairs of swimming legs, of which 

 the last is furnished with gills; and this hexagonal shield termin- 

 ates in a long pointed process (q). Now when we compare the 

 appendages to the head and body of these animals, with those of 

 ordinary Crustacea, it is evident that the first pair of the legs sur- 

 rounding the mouth of the Limulus represents their mandibles ; 

 that the second and third pairs represent their maxillae; the three 

 following pairs of legs their feet-jaws ; and the five pairs of 

 swimming-members, abdominal fin-feet, the true thoracic legs 

 being altogether absent. Besides the pair of compound eyes, 

 characteristic of the Crustacea in general, the Limuli have a pair 

 of small simple eyes, placed' anteriorly, near the central line. 

 The Limuli are confined to the shores of tropical Asia, the Asia- 

 tic Archipelago, and tropical America. As the best-known species 

 comes from the Molucca Islands, they are sometimes termed 

 Molucca Crabs. Of their habits very little has been ascertained. 

 They appear to prefer the neighbourhood of sandy shores, and it 

 is said that when kept from the water, they bury themselves in 

 the sand, in order to avoid the violent heat of the sun, which 

 causes them speedily to perish. They feed upon animal flesh. 

 The long process of the posterior shield is not developed in the 

 young animal ; which also wants the posterior branchial mem- 

 bers. This process is used by some of the Malays as a point 

 for their arrows; the wounds it makes being dangerous, like those 

 made by the spines of many Fishes, on account of their jagged 

 character. On the coast of America, where the Limulus is known 

 as the Casserole Fish, the shell is employed as a ladle for water. 

 Fossil remains of this genus are not uncommon in the Second- 

 ary and Tertiary strata ; and it may be further remarked that, 

 in several particulars, the Trilobites may be regarded as having 

 been probably analogous to it. 



