Classification of the Decapod Crustaceans. 4G9 



the rest. First antenure creuerally bear a 

 stylocerite. Second anteniinl scale generally 

 large. Leg's slender (except sometimes a 

 Btout chelate limb or pair which may beany 

 one of the first three pairs), with basipodite 

 and iscliiopodite never fu>ed, only one fixed 

 point in the carpo-propodal articulation, 

 sometimes exopodites, and podubranchs 

 hardly ever present on the first three pairs 

 and never on the last two. Male genital 

 opening almost always arthrodiHl. Abdo- 

 minal limbs 1-5 always present in full num- 



ber, well developed, and used for swimming. NATANTIA, 

 II. Rostrum often reduced or absent, depressed 

 if present. Body not compressed, generally 

 depressed. First abdominal segment dis- 

 tinctly smaller than the rest. No stylocerite. 

 Second antennal scale never large, generally 

 small or absent. Legs strong, the first 

 usually, the others never, stouter than their 

 fellows, basipodite and iscliiopodite almost 

 always fused in the first pair, generally also 

 in the others ; two fixed points in the carpo- 

 propodal articulation, exopodites never 

 present, podobranchs fairly often present on 

 some of the fir^t four pairs. Male genital 

 opening coxal or sternal. Abdominal limbs 

 l-o often reduced or absent, not used for 

 swimming REPTANTIA. 



Key to the Tribes of the Nataiitia. 



I. Third legs chelate, except in genera in which 

 the legs are much reduced. Third maxilli- 

 peds 7-joiuted. Second maxillipeds with 

 normal end-joints. First maxillipeds with- 

 out the caridean lube on the base of the 

 exopodites. Pleura of first abdominal seg- 

 ment not overlapped by those of second. 

 Abdomen without sharp bend. Not phyllo- 

 branchiate (except Amphionin.Te). 



1. Une or both legs of third pair longer and 



much stouter than those of first two pairs. 

 Trichobranchiate. Endopodites of first 

 maxillipeds short. Mandibular palps 

 curved. First antennse without stylo- 

 cerites. First abdominal limbs of male 

 not as in Penseides STENOPIDES. 



2. Legs of third pair not stouter than those of 



first two pairs. Dendrobranchiate (except 

 Leucifei'inae and Amphionina? : see below). 

 Endopodites of first maxillipeds long. 

 Mandibular palps straight. First antennae 

 generally with stylocerites. F'irst abdo- 

 minal limbs of male bear a sexual 

 apparatus PENjEIDES. 



