376 



ARTHROPODA 



The MYSIDID/E are widely distributed, several species of Mysis (fig. 396) 

 occurring on our coasts and one in the Great Lakes. In these the endopodite 

 of the sixth abdominal appendage contains a otocyst, with a calcic fluoride 

 statolith. Other families are the EUPHAUSIID.E and LOPHOGASTRID^; of the 



high seas. 



FIG. 396. Mysis elongata (from Gerstacker). , J3, first and second antennae; a, 

 expedite; au, eye; z, endopodite; o, otocyst; 1-7, abdominal somites. 



Order II. Stomatopoda. 



In structure of the cephalothorax these forms, known as mantis shrimps 

 (from a resemblance to the insect, the praying mantis), are lower than the 

 schizopods, since the last three or four thoracic somites are free and are not 

 covered by the carapace. The appendages, however, are more developed, 

 since only the three posterior of the thoracic feet are biramous and natatory. 

 The four in front of these are prehensile and bear a pincer formed of the last 

 two joints, the last being slender and usually toothed and closing in a groove of 

 the penult joint like a knife blade in the handle. The first of" these raptorial 



sac. 



FIG. 39j.Squilla mantis, at, at', first and second antenna?;/, sixth abdominal feet; 

 k, gills; p, schizopodal thoracic feet; pr, pr', raptorial feet; />\, pleopoda; sa, 

 telson. 



feet are the largest and are used in capturing fishes, etc. Since the thoracic feet 

 are of little service for locomotion, the abdomen is long and stout, especially the 

 caudal fin. The five anterior abdominal feet bear the gills, and correspondingly 

 the elongate heart with many ostia extends into the abdomen. The transparent 

 pelagic larvae were formerly regarded as adults and described as Alima and 

 Enchthus. Squill a* Gonodactylus* They are burrowing animals and deposit 

 their eggs in their holes. 



