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U.S. NATIONAIj museum bulletin 271 



Figure 47. — Isaeidae (incl. Photidae), pereopods usually glandular: a, coxa 4, note lack 



of posterior excavation (coxa 4 may be long or short) [see some Gammaridae, Pleustidae, 



Calliopiidae and related families]; b, extremes of accessory flagellum; c,d,e, variations in 



uropod 3;/, telson, thick, short, and fleshy [see Calliopiidae, Pleustidae, Oedicerotidaej. 



Five isaeid genera have uniramous uropod 3 and might be confused with numerous other 



gammaridean families having uncleft telsons. But Cressidae, Stenothoidae, and Thauma- 



telsonidae have reduced first coxae; Eophliantidae have cylindrical bodies; Phliantidae, 



TaHtroidea, and Dogielinotidae lack mandibular palps. Sebidae have subequally large, 



chelate gnathopods. Pagetinidae have evanescent mandibular molars and poorly developed 



outer plates of maxillipeds. See Aoridae, Ischyroceridae, Ampithoidae, Corophiidae, Podo- 



ceridae, and Cheluridae to follow for diagnostic differences. 



