ANNULOSA : CRUSTACEA. 241 



are distinguished by the possession of six pairs of chela te limbs, 

 placed round the mouth, having their bases spinous and officiating 

 as jaws. The anterior portion of the body is covered by a 

 broad horse-shoe-shaped buckler (fig. 90), the upper surface of 

 which bears a pair of larval and a pair of compound eyes. On 

 the lower surface of the carapace is placed the aperture of the 

 mouth, surrounded by six pairs of limbs, the bases of which 

 are spinous, and officiate as jaws, whilst their terminations are 

 converted into chelae or nipping-claws. The first pair of 

 appendages is placed in front of the mouth, and represents the 

 antennae, so that the antennae of the King Crabs are chelate. 

 Behind the cephalic buckler comes a second shield, composed 

 of six amalgamated segments, below which are carried the 

 reproductive organs and branchiae, the former protected by a 

 thoracic plate or " operculum," the latter borne by five pairs 

 of lamellar appendages. Lastly, articulated to the posterior 

 margin of the abdominal shield, is a long sword-like spine or 

 " telson " (fig. 90, /). 



The larval Limulus does not possess the ensiform post-anal 

 spine of the adult, and is further stated to show a decided 

 resemblance to the Trilobites. 



The King Crabs are found in the Indian and Japanese Seas, 

 on the coasts of North America, and in the Antilles. They 

 sometimes attain a large size, and both the eggs and the flesh 

 are eaten by the Malays. 



SUB-ORDER 2. EURYPTERIDA. " Crustacea with numerous, 

 free, thoracico-abdominal segments, the first and second (?) of 

 which bear one or more broad lamellar appendages upon their 

 ventral surface, the remaining segments being devoid of appen- 

 dages ; anterior rings united into a carapace, bearing a pair of 

 larval eyes (ocelli) near the centre, and a pair of large, mar- 

 ginal, or sub-central eyes ; the mouth furnished with a broad 

 post-oral plate, or metastoma, and five pairs of movable ap- 

 pendages, the posterior of which form great swimming-feet ; 

 the telson, or terminal segment, extremely variable in form ; 

 the integument characteristically sculptured " (Henry Wood- 

 ward). 



The Eurypterida are all extinct, and are entirely confined to 

 the Palaeozoic period. Many of them attained to a compara- 

 tively gigantic size ; Pterygotus Anglicus (fig. 91) being supposed 

 to have reached a length of probably six feet. In their char- 

 acters they present many larval features ; resembling the larvae 

 of the Decapoda especially in the fact that all the free somites 

 of the abdomen (except the two anterior ones) were totally 

 devoid of appendages. 



Q 



