MARINE GAMMARIDEAIsT AMPHIPODA 217 



mandibular palp or a simple gnathopod 1. Only Elasmopus, Liagocera- 

 docus, and Anelasmopus do not fit these statements. 



Though originally assigned to Amphilochidae, Pseudamphilochus 

 Schellenberg falls to the Eusiridae, especially through the illustrated 

 family key. That genus has the head of an amphilochid or pleustid, 

 gnathopods of an amphilochid, a lower lip faintly resembling that of 

 Pleustidae, but coxa 1 is not reduced as it is in Amphilochidae and the 

 cleft telson is unlike either pleustids or amphilochids. Pseudamphilo- 

 chus has been given a special place in Gammaridea Family Key G 

 (p. 114) and is mentioned also under the Amphilochidae. 



Lepechinellids have acuminate coxae and apparently always have 

 pleonites 5-6 coalesced. 



Key to the Genera of Eusiridae ^ 



1. Article 6 of gnathopods attached to the strongly produced or extended apex 



of article 5 ("Eusirus gnathopods"), article 6 as broad as long (figs. 



92b,e,h,j) 2 



Article 6 of gnathopods with normal attachment, article 6 longer than 

 broad (figs. 92a,c,d,i,m) 5 



2. Articles 4 and 6 of gnathopods touching (fig. Q2h), antennae with calceoli 



(fig. 89i) Eusiropsis 



Articles 4 and 6 of gnathopods not touching, separated by a lobe of article 

 5 (figs. 926, j), antennae lacking calceoli 3 



3. Article 6 of gnathopod 1 larger than article 6»of gnathopod 2, palp article 3 of 



mandible shorter or scarcely shorter than article 2 (fig. 90/) . Eusirogenes 



Article 6 of gnathopod 1 equal to or smaller than article 6 of gnathopod 2, 



palp article 3 of mandible equal to or longer than article 2 (fig. 90d) . . 4 



4. Posterior border of article 5 of gnathopods forming a very narrow projecting 



lobe, much narrower than length of tapered distal end of article 5 (fig. 



926) Eusirus 



Posterior border of article 5 of gnathopods formed of a broad, shallow setose 

 lobe, its length greater than the tapered distal end of article 5 (fig. 92e). 



Pareusirogenes 



5. Palp of maxilla 1 short, article 1 longer than 2 (fig. 91/) Eusirella 



Palp of maxilla 1 long, article 2 longer than 1 (fig. 91g) 6 



6. Articles 4, 5, 6 of pereopods 3-5 each 1.5 times as long as article 2 (if legs 



broken proceed to couplet 9) (fig. 89o) 7 



Articles 4, 5, 6 of pereopods 3-5 each as long as their second articles (fig. 

 896) 9 



7. Gnathopods not subchelate Harcledo 



Gnathopods subchelate 8 



8. Body carinate (often weakly), coxa 1 produced forward (fig. 89o). 



Rhachotropis 

 Body not carinate, coxa 1 not produced forward Cleonardo 



9. Epistome with large anterior process (seen from lateral view) 10 ^ 



1 Pseudopontogencia Oldevig (1959) and Pontogeneoides Nicholls (1938) are not sufficiently described for 

 inclusion in the following key. 



2 See also small process of Meteusiroides and broadly flabelliform (dorsal-ventral) but shallow process of 

 ChosToes and footnote 3 to couplet 31. 



