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NEW YORK STATE MUSEUM 



beach fleas or one of the common salt-water Gammarids will do as 

 well. 



In this form [fig.i] the fusion of the segments has not taken 

 place to the extent that it has in the crayfish. The head consists 

 of the prostomium and five fused segments, and to them is added 



Fig. i Diagram of Gammarus fasciatus 



Divisions of body : t>/=cephalon or head ; Per. =pereion, thorax or mesosome ; /Y=pIeon, 

 abdomen (the first three segments of this are sometimes called the metasome, the last three 

 urosome) 



Appendages of cephalon : >4Mr 1 =antennula or superior antenna; /Va^peduncle ; 77 1 =flage!- 

 lum ; Wc=accessory or secondary flagellum: ^4«/ 2 =antenna or inferior antenna; Ped^ped- 

 uncle ; J7 2 =flagellum ; M. ^=mandibular palp \Mx. /=maxilliped 



Appendages of pereion : GT/^first gnathopod ; Gwjj-second gnathopod ; />£*-. <f=pereiopoda 



Joints in all the legs ; C=coxa ; ^=basus; /= ischium ; J/=merus; Gz=carpus; /*=propo- 

 dus ; Z>=dactylus ; />a=palm of gnathopod 



Appendages of pleon ; Pl.d =p!eopoda ; £/>-=uropoda ; 7=telson 



| : — | = length of animal from front of head to end of terminal uropod 4=male 



? = female 



one thoracic segment, but there is no carapace. The remainder of 

 the segments are all free. 



The head bears a pair of sessile eyes, that is eyes without a stalk, 

 a pair of antennulae [Ant t ] and a pair of antennae [Ant 2 ]. Each 

 of these consists of a peduncle [Ped] of three and four joints 

 respectively and a flagellum [Fla] of many joints. In addition to 

 this, the antennulae bear a very short accessory flagellum [Ac]. The 

 mouth parts are quite similar to those of the crayfish, consisting of 

 mandibles and two pairs of maxillae. The mandibles in the Amphi- 



