48 PEOCEEDINGS OP THE GEOLOGICAL SOCIETY. [DeC. 20, 



that the Kmg- crabs of to-day trace back their ancestry at least 

 to Silurian, times. 



The following notes on the living King-crab, or Horsefoot-crab, 

 of N. America, Limtdus jooh/pJiemus, are extracted from Rev. Samuel 

 Loekwood's paper above cited. 



The modern Limulus inhabits moderately deep water (from 2-6 

 fathoms), and never seeks the shallows save for the purpose of re- 

 production. The young, however, being unable to resist the action 

 of the sea, are carried to and fro by the tide. 



Limulus is emphatically a burrowing animal, living literally in 

 the mud, into which it digs its way with great facility. It Uses 

 the front border of its head-shield (inflected at a sharp angle with 

 its hinder shield) for this purpose, aided by its tail, which serves as 

 a fulcrum. By the active use of its feet, and by alternately in- . 

 fleeting and straightening its carapace, it accomplishes both dig- 

 ging and subterranean progression. It is carnivorous in its habits, 

 feeding upon any of the soft-bodied Nereids and other mud-dweUing 

 annelides and mollusca which it meets with. 



Dr. Lockwood finds that the King-crab, when 'caught by one of. 

 its legs, does not attempt to free itself by casting ofi^ the impri- 

 soned limb, as a crab or lobster would do under similar circum- 

 stances. The leg of the Decapod, however, is not homologous 

 with that of Limulus, whose organs of locomotion are modified 

 palpi or maxillipeds rather than true feet, all its walking- appen- 

 dages being mouth-organs at their proximal end, which would render 

 their replacement in Limulus as difiicult as would be that of the 

 maxillae or maxillipeds in a Decapod Crustacean. 



It, however, exuviates like other members of the Crustacean 

 class, five or six times at very short intervals during the first 

 year, and afterwards about twice annually. 



From an actual experiment made by the Rev. Samuel Lock- 

 wood it would appear that the female King-crab spawns twice 

 every year, the breeding-season being during the months of May, 

 June, and July. They come up during the great high tides, spawn- 

 ing under water near the high-water mark ; thus the eggs are 

 daily exposed to the sun's -^armth for a short time at low water. 



At this season they come up in great numbers in pairs, the 

 male grasping the sides of the female's shield with his strong and 

 pecuharly modified chelate antennae. 



The eggs, measuring fully half a pint in quantity, and about the 

 size of millet seed, are deposited by the female in a hole in the 

 sand, and are fecundated by the male after deposition, and then 

 left to hatch. 



This is unlike the behaviour of any other of the Crustacea, which, 

 as a rule, appear to fecundate the ova by a true union before the 

 eggs are discharged from the ovaries*. 



The eggs, moreover, in the Crustacea (with the exception of 

 the genus Squilla and a species of Gecarcinus) are usually borne by 



* [According to a paper read by M. Chantran to the French Academy of 

 Sciences on January 15th, 1872, the eggs of thcj ommon Crayfish are fecundated 

 after expulsion from the oviducts. — Ed. Q. J. G. S.] 



