pods present, with exopods absent or present 

 only as rudiments; six-segmented abdomen fol- 

 lowed by telson and biramous uropods; five pairs 

 of setose, functional pleopods present (Post- 

 larvae) 15 



12(11) First three pairs of pereiopods cleft to form 

 rudimentary chelae; pleura of first abdominal 

 segment overlap second; antennal blades present; 

 pleopods develop on first five abdominal segments 

 simultaneously although they are not necessarily 

 of equal length; telsor narrow and notched 

 medianly; uropods without statocysts; usually, 

 no spines originate from posterior half of carapace 

 and margins of carapace not serrate ; if spines or 

 serrations present, a dorsal organ also present 



(Penaeid mysis fig. 3) 13 



One or more of following characters present: 

 first three pereiopods not cleft to form rudi- 



1 Rostrum 



2 Rostral Spine 



3 Supraorbital Spine 



4 Hepatic Spine 



5 First Antenna 



6 Antennal Blade 



7 Chela 



8 Exopod ol Pereiopod 



9 Dorsal Abdominal Spine 



10 Lateral Abdominal Spine 



11 Telson 



12 Uropod 



mentary chelae; pleura of second abdominal 

 segment overlap first; antennal blades absent; 

 pleopods may not be present on all abdominal 

 segments; telson broad and fan shaped or not 

 notched medianly; uropods with statocyst; 

 spines originate from posterior half of carapace or 

 margins of carapace serrate, with no dorsal organ 

 present Nonpenaeid mysis 



13(12) Pleopods absent Mysis I (fig. 3a) 



Pleopods present 14 



14(13) Pleopods small and unjointed._ Mysis II (fig. 3b) 

 Pleopods long and jointed Mysis III (fig. 3c) 



15(11) First three pairs of pereiopods chelate; pleura of 

 first abdominal segment overlapping second; 

 five pairs of functional pleopods present; gills 

 covered by carapace; antennal blades present 



Penaeid postlarva (fig. 4) 

 One or more of the following characters present: 

 first three pairs of pereiopods not chelate; pleura 

 of second abdominal segment overlapping first; 

 less than five pairs of functional pleopods present; 

 gills extending from beneath carapace; antennal 

 blades absent Nonpenaeid postlarva 



Figure 3.- — Penaeid myses: a, Mysis I; 6, Mysis II; c, 

 Mysis III. 



1 Rostrum 



2 Antennal Sptr 



3 Hepatic Spin* 



4 Ptetygostomi 



5 Cetvical Sulcus 



t. Anlennule 



7 Endopod of Pleopod 



8 Eiopod ol Pleopod 



9 Telson 

 10 Pleuton 



Figure 4. — Penaeid postlarva. 



PENEIDAE OF THE NORTHWESTERN GULF OF MEXICO 



441 



