epistome (anterior) and ventrolateral extensions 

 of carapace (each side) more or less thrown into 

 ridges forming a "frame" for nested mouthparts. 



front margin of carapace between eyes (in crabs). 



hepatic region subtriangular, anterolateral region 

 behind orbit. 



interocular teeth teeth on frontal margin between 

 eyes. 



ischium fifth article from distal end of leg or maxil- 

 liped; usually largest article of maxilliped. 



mandibles third pair of appendages; mouth parts 

 adapted for crushing or grinding. 



merits fourth article from distal end of leg or maxil- 

 liped. 



orbit cavity or emargination in carapace accom- 

 modating eye; variously formed. 



Commencing orbit: a stage of specialization 

 between lack of orbit and fully formed orbit in 

 certain spider crabs. 



palm proximal portion of propodus of chela. 



palp tiny accessory appendage on mandible. 



pleopod swimmeret; one of biramous abdominal 

 appendages on any except sixth segment. 



pleura lateral overhanging plate on abdominal 

 segment. 



postorbital tooth - spine tooth or spine behind eye . 



propodus penultimate article of leg or maxilliped. 



rostrum median pointed process at anterior end of 

 cephalothorax. 



sclerotized thickened and hardened. 



sternite exoskeletal plate on ventral side of body. 



supraocular eave overhanging dorsal border of 

 orbit (in certain spider crabs). 



supraorbital spine spine near margin of orbit above 

 base of eyestalk (in certain shrimps). 



suture line of junction between exoskeletal plates. 



telson terminal piece attached to end of sixth ab- 

 dominal segment; forms, together with uropods, a 

 tail fan. 



tergum dorsal plate on abdominal segment. 



third maxilliped appendage preceding first leg. 



thorax central portion of body to which legs and 

 maxillipeds attach. 



uropods broad paired appendages on sixth abdom- 

 inal segment; often forming, together with telson, 

 a tail fan. 



adrostral groove 



tergunv- 



m 



cheli 



>ropodus 



Hegs- 



-dactyl 



pleopods_ 



Figure 1. — Diagram of shrimp in lateral view showing structures and terms used in key. 



-telson 



-uropod a 

 n 



