JETSAM OF MANTIS SHRIMPS. 33 



bods of the Laminarian zone had been devastated by heavy surf due 

 to the bursting of storms coincident with the furthest receding tides 

 of the year, and the Squillids forced or frightened from their burrows, 

 and helpless to withstand or get clear of the dashing breakers, had 

 been buffetted to and fro, to be finally thrown in multitudes upon 

 the beach. 



The Squillidse, the sole members of the order Stomatopoda^ are 

 distinguished from the other order of large Crustaceans the Deca- 

 poda (Lobsters, Crabs, &c.) by a different arrangement for breathing 

 and by a different function to which certain of the anterior limbs 

 are put. 



For the purpose of comparison, let us take the Lobster as type of 

 the Decapoda. In it, the three divisions of the body of an ideal higher 

 crustacean head, thorax and abdomen are reduced to two, by the 

 fusion of head and thorax to form the cephalothorax. This, pro- 

 tected by a great shield, the carapace, is furnished with 14 pairs of 

 appendages. Taking these in order from before backwards, we have 

 one pair of stalked and moveable compound eyes ; two pairs of 

 sensory organs, the antennae ; one pair of stout jaws or mandibles ; 

 two pairs of weaker jaw organs, maxillae ; followed by three pairs of 

 appendages which in structure are midway between that of the 

 walking limbs and that of the maxillae, and as they share in the work 

 of preparing food and closely surround the mouth, they have received 

 the name of foot-jaws, or maxillipeds. Next come five pairs of large 

 walking or ambulatory limbs, pereiopods. Of these, the anterior pair 

 are enormously enlarged and form the chelae, or pincers, powerful 

 organs for seizing and tearing prey. The second and third pairs have 

 also small pincer terminations, but the third and fourth end in 

 simple claws. 



The abdomen consists of five well-marked rings or somites, 

 bearing each a pair of two branched (biramous) swimming feet or 

 swimmerets, followed by another somite bearing much enlarged 

 flattened swimming feet. A large, strong plate, telson, forms the 

 hinder extremity of the body and with the plate-like limbs of the 

 preceding somite, constitutes a powerful flapping tail the so-called 

 caudal fin. In all probability, the telson represents a true somite 

 once provided with swimmerets, for the anus opens on the under side 

 of it, and further, minute moveable points, esteemed to be vestiges of 

 swimmerets, have been observed upon the telson of the common 

 prawn, Palcvmon serratus* If this be so, the abdomen consists of 

 seven somites ; and as each pair of limbs attached to the cephalothorax 

 is believed to indicate an original somite, we arrive at 14 as the 



* Bell, History of Br. Stalk-eyed Crustacea, p. xx., London, 1853, 



