MARTNiE GAMMARIDEAIN AMPHIPODA 37 



incisor, a lacinia mobilis formed of a thin lamina resembling the incisor 

 and nearly appressed to it, plus a molar bulge clearly moved distal- 

 wards toward the incisor and nearly or partially encroached upon by 

 the spine row. One group of stenothoids has the amphilochid coxa 1, 

 whereas the other has the leucothoid (normal) coxa 1. Sebid 

 gnathopods even vaguely resemble gnathopod 1 of leucothoids and 

 numerous other similarities are apparent. Stenothoidae, Thaumatel- 

 sonidae, and Cressidae, those with amphilochid coxa 1, are very 

 closely related among themselves, even though some extremely 

 pygidized species have been used as types of the Thaumatelsonidae 

 and Cressidae. The five stenothoid families are obviously inter- 

 related through the condition of uropod 3. It is uniramous, pre- 

 sumably through loss of the inner ramus, as the remaining ramus is 

 basically biarticulate. Neither the Leucothoidae nor Amphilochidae 

 show a tendency to this condition, except perhaps for the universal 

 genus Pseudamphilochus. If the Amphilochidae were the precursors 

 of the Stenothoidae and the Leucothoidae were precursors to the 

 Sebidae, then the evolution of a common uropod 3 had to occur twice . 

 The superfamily Talitroidea, comprising originally the Talitridae, 

 for nearly a century have been considered as extremely distinct 

 gammarideans, often worthy of even subordinal rank. They are more 

 diverse than they ever have been if one were to add the Dogielinotidae 

 and Kuriidae to their ranks and to suggest that Najna and Metoediceros 

 represent types of new talitroid families. Bulycheva (1957) split the 

 Talitridae into three families, adding the Hyalidae and the Hyalellidae. 

 The three main families are here treated as a superfamily, mainly for 

 convenience in identification. Talitroids have no universally unique 

 characters; several other families have a uniramous uropod 3 and no 

 mandibular palp but among the genera of talitroids are many unusual 

 morphs. Often the cephalic sclerites are clearly marked. Numerous 

 gnathopodal, pleopodal, and antennal modifications occur in terrestrial 

 genera; the jumping ability is extreme in those genera. The marine 

 members appear more regularized, some even having vestigial inner 

 rami on uropod 3. Perhaps the structure of fringing setae on the female 

 brood lamellae will prove to be characteristic of the group. Although 

 they may be considered as very distant from the basic gammaridean, 

 their singularity is damaged by discovery of the Beaudettiidae. That 

 monotypic family is composed of a species with clear relationship to 

 Elasmopus, a member of the Gammaridae. Through loss of mandibular 

 palp, reduction of the inner ramus of uropod 3, and telsonic modifica- 

 tion, Beaudettia has come close to the talitroidean grade of Structure. 

 Morphological distance of talitroids from gammarids, as a reflection 

 of time or extensive genetic change, is thus lessened by our 

 observation of the revolutionary changes that have occurred in 

 Beaudettia, possibly in relatively recent times. 



