Decapod Crustacea of the Californian and Oregonian Zoogeographic Provinces 3371 Author Wicksten, Mary K. text Zootaxa 2012 2012-07-04 3371 1 307 journal article 1175­5334 Key to Species of family Palaemonidae 1. Posterior margin of telson with 2 pairs spines. Pleurobranch on third maxilliped. Rostrum always with teeth.............. 2 – Posterior margin of telson with 3 pairs spines. No pleurobranch on third maxilliped. Rostrum with or without teeth........ 4 2. Carpus of pereopod 2 distinctly shorter than chela. San Diego, California south........................ Palaemon ritteri – Carpus of pereopod 2 longer than chela. San Francisco Bay south............................................... 3 3. Rostrum with subapical tooth, mandible with palp. Total length can exceed 25 mm ............... Palaemon macrodactylus – Rostrum without subapical tooth, mandible without palp. Total length reaching 25 mm .............. Palaemonetes hiltoni 4. Rostrum without dorsal teeth............................................................................ 5 – Rostrum with dorsal teeth............................................................................... 6 5. Body stout, major chelipeds heavy, lobster-like. Symbiotic with ascidians..................... Ascidonia californiensis – Body, major chelipeds slender. Not symbiotic with ascidians................................ Pseudocoutierea elegans 6. Rostrum arched over eye, carapace without supraorbital teeth................................ Periclimenesinfraspinis – Rostrum not arched over eye, carapace with supraorbital teeth................................. Palaemonella holmesi