18 University of California Publications in Zoology [Vol. 23 



III. SYSTEMATIC DISCUSSION OF THE CALIFORNIA 

 REPRESENTATIVES OF THE ORDER DECAPODA 



Key to the Suborders of the Decapoda 



I. Body almost always laterally compressed (macrurous, shrimp-like). First 

 abdominal segment not much smaller than the rest. First antennae usually 

 having a scale at base; second antennae with scale generally large and 

 lamellar. Legs usually slender except sometimes a stout chelate limb or 

 pair, which may be any one of the first three pairs, with basipodite and 

 ischiopodite never coalesced, and only one fixed point in the carpo-propodai 

 articulation. Male genital apertures in the articular membrane between the 

 coxopodites of the last (fifth) pair of legs, and the body; female genital 

 apertures on the coxopodites of the third pair of legs, (except in one genus, 

 Leucifer, not represented in California fauna; the sex of ovigerous females 

 is self-evident). Pleopods always present in full number, well developed, 

 and used for swimming. 



Natantia, p. 18. 



II. Body not well compressed, usually depressed (anomurous, hermit-crab-like, or 

 brachyurous, crab-like, rarely macrurous, shrimp-like). First abdominal 

 segment distinctly smaller than the rest. First • antennae without a scale; 

 second antennae, scale generally small or absent. Legs strong, first pair 

 usually stouter than their fellows, others never so, basipodite and ischio- 

 podite almost always coalesced in the first pair and generally in the others; 

 two fixed points in the carpo-propodal articulation. Male genital apertures 

 on the coxopodites of the last (fifth) pair of legs or on the sternum of the 

 corresponding somite; female genital apertures on the coxopodites of the 

 third pair of legs or on the sternum of the corresponding somite (the sex 

 of ovigerous females is self-evident). Pleopods often reduced or absent, 

 rarely used for swimming. 



Beptantia, p. 104. 



Suborder Natantia 

 Key to the Tribes op the Natantia 



I. Pleura of second abdominal segment overlap those of first ; abdomen generally 

 with sharp bend. Third legs not chelate. 



Carides, p. 26. 

 II. Pleura of first abdominal segment not overlapped by those of second; abdomen 

 without sharp bend. Third legs chelate. 



A. Legs of third pair not stouter than those of first two pairs. 



Peneides, p. 19. 



B. One or both legs of third pair longer and much stouter than those of first 



two pairs. (No representatives of this group found in the region cov- 

 ered by this paper.) 



Stenopides. 



