2 (/ ) Pleura of second abdominal segment overlapping those of first segment Section Caridea 



Figure 3. — Penaeidean abdomen, 

 lateral view. 



Figure 4. — Caridean abdomen, 

 lateral view. 



3 (2) First 3 pairs of legs chelate, all 5 pairs of legs well developed Family Penaeidae 4 



3 (2) First 3 pairs of legs chelate, last 2 pairs of legs absent; slender planktonic species with 



head greatly elongate Family Sergestidae Lucifer faxoni 



Figure 5. — Lucifer faxoni: carapace and 

 head appendages, lateral view. 



4 (3 ) Rostrum with ventral teeth Penaeus 



A (4) Adrostral grooves not extending be- 

 yond base of rostrum P. setiferus, 



white shrimp / -^- 



Figure 6. — Penaeus setiferus; \ 3 10 



carapace, lateral view. 



A (4) Adrostral grooves reaching almost to 



posterior margin of carapace 



P. aztecus aziecus, brown shrimp 



Figure 7. — Penaeus aztecus aztecus; \ — '0 



carapace, lateral view. 



4 (-?) Rostrum without ventral teeth; carapace 

 with both longitudinal and transverse su- 

 tures Parapenaeus longirostris 



Figure 8. — Parapenaeus longirostris; ^*%& i_ 



carapace, lateral view. 



5 



