Little research seems to have been done on west-coast shrimps and prawns, other than that relating to fisheries, so most attention in this section of the ODYSSEY will be on burrow-inhabiting forms (mud and ghost shrimps). These forms are no more closely related to shrimps than they are to many other decapod crustaceans but, for convenience, will be included in this section.  There are 3 main species of thalassinids (mud and ghost shrimps) and about 20 species of shrimps and prawns on the Pacific west coast, about one-quarter of which are commercially important. 

NOTE  so named because of their pale whitish-yellow or pale pink colour

NOTE  if you are wondering about the difference between “shrimp” and “prawn”, perhaps the following will help (...or not): 1) the older of the two names, schrympe or shrimpe (likely from the German “schrimpen” meaning to “shrink up”), has been in recorded use from the 14th C., while the word “prawn” has had a more recent origin , 2) shrimps are mostly swimmers while prawns are mostly walkers and, 3) shrimps are thought to be smaller and prawns larger.  The last is made clear in an entry from the Daily Telegraph newspaper in London in 1865 which states: “Our shrimps have most prawny proportions”.  If this is still not clear, you can join the authors who get around the problem by referring to them all as shrimps; in the ODYSSEY, they'll be referred to generally by the name used by the author of the particular research study being considered

Shrimps/prawns along with isopods, crabs, barnacles, and amphipods (in order of appearance in the ODYSSEY) are classified in the Subphylum Crustacea in the Phylum Arthropoda:

Phylum Arthropoda (lit. “jointed legs” G.)

Subphylum Crustacea (lit. “crust or rind” L.), referring to the hard calcified exoskeleton

Class Malacostraca includes all the “advanced” crustaceans

Order Decapoda (lit. “ten feet” G.), referring to the presence of 10 legs that characterises the Order (includes crabs, shrimps, lobsters)
        
         Suborder Pleocyemata

Infraorder Thalassinidea (lit. “sea” G.), including mud (Upogebia pugettensis) and ghost (Neotrypaeaspp.) shrimps

Infraorder Caridea (lit. “shrimp” L.), shrimps and prawns, including Families Pandalidae (e.g., coonstripe shrimp Pandalus danae), Thoridae (Hyppolytidae or broken-back shrimps), and Sergestidae, the last including Eusergestes similus, a midwater-inhabiting vertical-migrating species

NOTE  formerly “Callianassa”, two species of which co-occur along the west coast from Alaska to Baja California: N. californiensis and N. gigas.  Researchers in California separate the species using genetic (allozyme) markers and provide a handy morphological distinguishing feature: length and shape of the distal outer edges of the eyestalks (see drawings).  Pernet et al. 2010 J Crust Biol 30: 323.