KEY TO GENERA AND SPECIES OF LATREILLIIDAE STIMPSON, 1858

1. Last pair of pereopods (P5) smooth, without conspicuous setae on propodus (Fig. 2); propodus of P5 half or less than half total length of carpus .................. Eplumula (2)

— Last pair of pereopods (P5) with conspicuous setae along full length of propodus, giving it feather-like appearance (Fig. 1); propodus of P5 clearly more than half total length of carpus .................................................................................... Latreillia (3)

2. Absence of spine on each branchial region of carapace of adults. Dorsal surface of gastric region of carapace (“neck”) without a spine except in large females; ventral surface of meri of third maxillipeds without a spine or tubercle (Fig. 3A) except some large females; Australia, New Caledonia, and New Zealand ................ E. australiensis

— Acute spine on each branchial region of carapace of adult females. Dorsal surface of gastric region of carapace (“neck”) always with a spine; ventral surface of meri of third maxillipeds with an acute spine, particularly in females; acute spine on each branchial region of adult females; Japan to the Philippine Islands ...... E. phalangium

3. Dactyli of last pair of pereopods (P5) trail, not forming subchelae (Figs 10; 12) .... 4

— Dactyli of last pair of pereopods (P5) forming subchelae by closing against distal portion of propodi, which have spinules (Fig. 6) ........................................................ 5

4. Dorsal surface of gastric region of carapace with spine. Gastric region short in relation to rest of body, its length less than 0.35 of carapace length (Fig. 12); Indo-west Pacific region .............................................................................................. L. valida

— Dorsal surface of gastric region of carapace without spine (prominence may be present). Gastric region slender in relation to rest of body, its length more than 0.35 of carapace length (Fig. 10); Indian Ocean and western Pacific .................. L. pennifera

5. Abdominal somites 4-5 of males fused; Atlantic coast of southern South America .... .............................................................................................................. L. williamsi

— Abdominal somites 4-5 of males distinct, not fused................................................ 6

6. Dorsal surface of gastric region of carapace with well defined spine in juveniles and many small adults; Indo-west Pacific and eastern Pacific regions ............ L. metanesa

— Dorsal surface of gastric region of carapace without well defined spine, rarely in juveniles and small adults, although prominence may be present; Mediterranean Sea and eastern and western Atlantic Ocean............................................................ L. elegans