THE CRUSTACEA OF NEW JERSEY. 309 



of the principal kinds of food for shad, spotted flounder and 

 mackerel, besides other fishes. Adult examples are only about an 

 inch in length. The animal is nearly transparent, whitish, with 

 prominent black eyes, and a row of more or less pronounced dark 

 stellate spots along body, both above and below, with similar 

 specks often on tail. Spot of dark-brown or blackish often oc- 

 curs on each side of carapace. The intestine shows through as 

 greenish or brownish line. 



Order DECAPODA. 



The S talk-By ed Crustacea. 



Thoracic segments united with head to form cephalothorax 

 usually covered by carapace. Eyes on stalks, movable. Mouth 

 armed with mandibles and jaws for mastication. Third maxilli- 

 peds leg-like. Three anterior pairs of thoracic lines biramous 

 foot-jaws, and posterior five pairs walking-legs without exopo- 

 dites. So-called gills generally present, thoracic. 



This great group includes the larger and higher forms. Three 

 divisions are here admitted as sub-orders, as the transition be- 

 tween the Macrurans and Brachyurans is gradual and indistinct. 



Key to the Sub-Orders. 



a. Abdomen usually shorter than cephalothorax, and commonly held in an 

 extended position ; usually distinct rostrum present ; eyes not enclosed in 

 orbits ; antennules and antennae large ; antennules not sunk in pits ; an- 

 tennae with an exopodite or squame. 



b. Abdomen equally or better deveoped than cephalothorax, behind which 

 more oi« less completely extended and beneath which never per- 

 manently flexed, ends in large symmetrical tail-fan with almost 

 always foliaceous lateral lobes (caudal swimmerets) ; front not joined 

 with epistome; thoracic sternurrt usually narrow, if broad last seg- 

 ment not independently movable, genital ducts never open on sternum ; 

 antennal peduncle commonly with a movable foliaceous exopodite, 

 though not always present. macrur.\ 



.bb. Abdomen less developed than cephalothorax, exceptionally elongate, 

 symmetrical, extended in straight line behind cephalothorax when 

 either rolled on itself or flexed against sternum or coiled spirallv, in 



