EURYPTERIDA. 



381 



Eurypterus, the anterior portion of the body is covered by a 

 buckler or carapace, which bears a pair of minute larval eyes, 

 and a pair of large compound eyes placed marginally or sub- 

 centrally. On the under surface of the carapace are five 

 pairs of appendages. The first pair of these is usually re- 



Fig. 238. Xiphosura. Limulus poly- 

 pliemus, viewed from below, c, The 

 cephalic shield carrying the sessile eyes 

 upon its upper surface; o, "Operculum," 

 covering the reproductive organs; b, 

 Branchial plates ; a, First pair of anten- 

 lue (antennules) ending in chelae. Below 

 these is the aperture of the mouth, sur- 

 rounded by the spiny bases of the re- 

 maining five pairs of appendages, which 

 are regarded by Woodward as being 

 respectively, from before backwards, 

 the great antennse, the mandibles, the 

 first maxillae, the second maxillae, and 

 a pair of maxillipedes. All have their 

 extremities chelate. 



Fig. 239. Eurypterida. Pterygotus 

 Anglicus, restored (after H. Wood- 

 ward), c, c, Chelate antennae ; o, o, 

 Eyes, situated at the anterior margin 

 of the carapace ; m, m, The mandi- 

 bles, and the first and second maxillae ; 

 n, n, The maxillipedes the basal mar- 

 gins of these are serrated, and are 

 drawn as if seen through the meta- 

 stoma or post-oral plate, which serves 

 as a lower lip. Immediately behind 

 this is seen the operculum or thoracic 

 plate, which covers the two anterior 

 thoracic somites. Behind this are five 

 thoracic and five abdominal somites ; 

 and lastly, there is the telson (). 



garded as representing the antennae. The appendages of 

 this pair are mostly chelate, or converted into nipping-claws, 

 but they are sometimes simple, and they sometimes are spin- 

 ous towards their bases, and officiate as masticatory organs 

 (Eurypterus and Slimonia). The next three pairs of appen- 



