MARESnE GAMMARIDEAN AMPHIPODA 47 



few genera of Eusiridae also have a nontriturative molar and thus 

 resemble Liljeborgiidae; but those genera lack an accessory 

 flagellum entirely; furthermore their gnathopods are unlike those of 

 Liljeborgiidae. 



Example 2: J^usiridae (fig. 39) differ from the basic gammaridean 

 only by the reduction of the accessory flagellum to 0-2 articles shown 

 in solid lines and by the elongation of the telson. Also figured in the 

 box is the lower lip in broken lines to show a distinction from the 

 Pleustidae and the Astyridae; uropods 1 and 2 in broken lines show 

 a distinction from the Liljeborgiidae and the illustrated telsons differ 

 from those of the Calliopiidae. 



Thus, the vestigial eusirid accessory flagellum is shared with many 

 other families but the special combination of basic gammaridean 

 morphology plus the telson, uropods, and lower lip is distinctive. 



Also, an inference is made on the caption that the student refer to 

 the figures of the Vitjazianidae (fig. 34), and the Oedicerotidae (fig. 27) 

 for characters distinguishing those families from the Eusiridae, i.e., 

 the simple first gnathopod and conjoint primary flagella of antenna 1 

 in the Vitjazianidae and the disproportionately long fifth pereopod in 

 the Oedicerotidae. 



Not mentioned are other deviations, such as the occasional reduc- 

 tion of mandibular molars and 1-articulate first maxiUary palps. 

 Several other families share these characters and may be partially 

 defined by them, but those families may be distinguished from the 

 Eusiridae by more important characteristics. 



Example 3: CaUiopiidae (fig. 38) differ from the basic gammaridean 

 only in the reduction of the accessory flagellum to 0-1 article and the 

 coalescence of the telsonic lobes. Also illustrated are the lower lip 

 which differs from that of the Pleustidae, coxa 4 to show a distinction 

 from the Isaeidae (=Photidae) and telsons to show faint distinctions 

 from the Eusiridae. Some calliopiids have isaeid-like coxa 4 but their 

 telsons are not fleshy and their pereopods lack glands. 



Example 1^.: The diagnosis of Amphilochidae (p. 132) includes 

 only: "Accessory flagellum absent; coxa 1 very small, partially hidden 

 by following coxae." Next is stated "See [the family] Pleustidae. ..." 

 The description of that family implies that coxa 1 is "normal" in size 

 and placement. In sequence, the description of the mentioned Steno- 

 thoidae should be examined to see that uropod 3 is uniramous and 

 therefore distinct from uropod 3 of the Amphilochidae. 



The Diagrammatic Key to Families is, at best, a method of narrow- 

 ing the search for a familial identiflcation to a few possibilities, each 

 textual diagnosis and description of which must be examined for good- 

 ness of fit. A flexibility has been maintained in the diagrammatic key 

 because of space limitations in presenting a compact visual impression 



