GAMMARIDEAN AMPHIPODA 183 



2. Lobes of maxilla 2 equal in breadth 3 



Inner lobe of maxilla 2 nearly twice as broad as outer 4 



3. Male antenna 2, flagellum greatly elongated . . . ?Pronannonyx and Aruga 

 Male antenna 2, flagellum not longer than in female Lysianopsis 



4. Maxilla 1, outer plate with 2 kinds of spines Arugella 



Maxilla 1, outer plate with 1 kind of spines "Lysianassa" 



As shown in the diagnoses and key above, the genera allied to 

 Lysianassa plumosa display a bewildering array of morphological 

 intergradations suggesting the necessity for their reduction to, at 

 best, subgeneric positions. Even this status fails a test as the fol- 

 lowing discussion intends to show. Unfortunately, "official" imple- 

 mentation of this revision cannot be activated until the type species 

 of Lysianassa is rediscovered and described adequately. The char- 

 acteristics used to distinguish the genera in the past are as follows: 



Maxilla 1. — The inner plate bears no primary setae in Lysianassa 

 plumosa, Shoemaker ella, and Arugella, and 2 setae in Lysianopsis, 

 Aruga, and IPronannonyx. The outer plate bears a single set of ser- 

 rated spines in L. plumosa and Shoemakerella, an accessory set of 

 partially bifid, slightly smaller spines in Lysianopsis, Aruga, and 

 Pronannonyx, and an accessory set of very small bifid spines in 

 Arugella. The drawings of the various type species generally show 

 7 large spines but only in Lysianopsis, Arugella, Aruga, and Pro- 

 nannonyx have the additional 4 spines been discovered, leading to 

 the suggestion that they may be present in the remaining genera and 

 species but were overlooked or considered to be spines of the sub- 

 sequent instar. Arugella was characterized by its exceedingly slender, 

 bifid set of secondary spines, but intergradation to stout, serrated 

 spines is seen in several other species: Aruga oculata, A. dissimilis, 

 and Lysianassa pariter, n.sp. 



Maxilla 2. — The inner plate of Shoemakerella is broadly flabellate 

 and twice as broad as the outer plate. That of Lysianassa plumosa 

 is sublanceolate and twice as broad as the outer plate. The inner 

 plate of Arugella and Pronannonyx is similar to that of L. plumosa 

 but is only slightly broader than the outer plate. Both Lysianopsis 

 and Aruga bear subequally broad plates. The conditions of this 

 mouthpart in Shoemakerella, L. plumosa, and Lysianopsis- Aruga are 

 sufficiently distinct for generic segregation, but Arugella forms a 

 transitional stage between Lysianassa and Aruga-L^ysianopsis. To a 

 degree this reduces the significance of the condition in Shoemakerella. 

 Lysianassa hypocrita is highly aberrant in its second maxilla. 



Maxilliped. — The very short, nearly vestigial fourth maxillipedal 

 palp article in Arugella heterodonta might be significant generically, 

 but there is considerable variation in the length of that article in the 

 other genera. Lysianassa hypocrita resembles Arugella in this regard 



280-102 0-69— 13 



