The maxillipeds are highly reduced compared to the gammaridean 

 prototype. They always lack a palp and are weakly armed. In many 

 Physosomata the maxillipeds are fairly large and stout; their inner lobes 

 are completely separated and the large outer petaloid lobes bear apical 

 and subapical setae {Mimonectes, Mimoscina, Microphasmoides). In the 

 Lanceola and related genera the inner lobes are relatively small but sep- 

 arate, in many Vibilioidea and Phronimoidea, contrarily, these lobes may 

 be as long as the outer lobes but are fused, forming a single plate, some- 

 times strongly armed with setae and spines. In the Scina and many Hyper- 

 iidae the fused inner lobes are much shorter than the outer lobes and are 

 armed with weak apical setae, while in the Acanthoscina and some other 

 genera of the group Phronimoidea {Bougisia, lulopis, Hyperietta, Themis- 

 tella) they totally disappear. The outer lobes may be petaloid and large 

 (as in Mimonectes), or narrow but well armed (Vibilioidea, Phronimop- 

 sis, Phronima); sometimes these are reduced to two small rectangular 

 plates attached to the distal angle of the basipodite {Acanthoscina) or 

 may be totally absent (Dairella). Finally, both the outer and inner lobes 

 may be fused into a single plate (Paraphronimidae). The labium is bilo- 

 bate, usually weakly developed, and reduced to some degree. In some 

 groups the complement of mouthparts is very prominent, forming the 

 so-called "mouth cone". 



Each of the seven thoracic somites bears a pair of seven-articled 

 pereopods. The articles are generally not designated by name but by num- 

 bers from 1 to 7. The 1st — coxal article — is modified into a dilated plate, 

 usually free, sometimes fused with the corresponding pereon somite. 

 Coxal plates are usually small, entire, and unlike in gammarideans, never 

 enlarged, do not cover each other, nor do they form a lateral shield. 

 Very rarely, coxal plate V is produced into a strong and pointed spine 

 (Acanthoscina, Spinoscina, Amphithyrus bispinosus, Platyscelus arma- 

 tus). In many Platysceloidea the 2nd article of pereopods V,VI, and 

 some-times VII is highly enlarged and broadened, becoming "squami- 

 form", and foi:ms a part of the lateral shield. In several groups pereopods 

 VII are somewhat reduced — in some they become very weak and short 

 (in some Scina), while in others some articles (4th and 5th, or 3rd, 4th 

 and 5th) are fused or disappear entirely. Reduction of pereopods VII is 

 extreme in the Platyscelus and Phrosina, in which the 2nd-3rd articles 

 are present, while in ihe Rhabdosoma only the 2nd article is present. 



Pereopods I and 11 may be simple, with a subchela (pseudochela) 

 or a well-developed chela; usually the clawlike formations are more 

 developed in pereopods II. The shape and structure of the distal (4th-6th) 

 articles of pereopods I and II constitute an important taxonomic character. 

 Pereopods III and IV are identical in structure, simple, with thin or fairly 

 19 thin articles; they are longer than pereopods I and II. Their 6th article 



