Stnntinr nf (he Mouth in Siicl-inf/ CrusUicfia. 'M)^t 



\)a\v of" iiKixilliV aiv cnclosi'd within the tul)i' and have assumed 

 a shape adapted to action inside it. Whilst, tliercfore, the 

 rostrum in Isopofhi contains niandil)h's and the Hist pair of 

 maxilla?, Lnphi/stius occupies the important staj^e in the deve- 

 lopment of the sucking-mouth in Crustacea where the rostrum 

 only contains mandibles. The oral formula for Laj)hi/st{us 

 will consecpiontly be the following. 



Laphystius. 



Os haustellum. 



Ilaustellum adversum clypeo labroque, aversum labio malisque 

 exterioribus ])edum maxillavium confectum, malas man- 

 dibulares scrratorias involvens, 



Clypeus rotundate quadratus, fornicatus, pendulus. 



Labrum maximum, productimi, conicum, acuminatum, fornica- 

 tiira, pendulum. 



Mandihuke stipite producto, angusto, acuminato, depresso, 

 mobili, basi palpigero, malis binis. Mala exterior sub 

 labrum oblique inHexa, fixa, in orificium haustelli deor- 

 sum eminens, linearis, margine terminali arcuato, serrato. 

 Mala interior basi malfe extcrioris inserta, membranacea, 

 mobilis, minuta, linearis, apice trifida. Palpus clypeum 

 amplectens, triarticulatus, pervalidus, articulo terminali 

 inter antennas recepto, producto, conico, acuminato, in- 

 trorsum breviter setigero. 



Maxilla' priorcs laminata^, malis binis, palpigerw. Mala exte- 

 rior i'-dlcata, apice s])inis longioribus,validioribus, incurvis, 

 in series binas redactis armata. Mala interior brevis- 

 sima, conica, apice parce spinigera. Paljms perexiguus, 

 conicus, singulo constans articulo, conico, apice truncato, 

 breviter biseto. 



Ma.rilliv posteriores laminata?, malis binis. Mala exterior 

 linearis, apice spinigera. Mala interior fiilcata, margine 

 intcriore parce spinifero. 



Pedes maxillares cardinibus stipitibusque concretis, productis, 

 fornieatis, malis binis, palpigeri. Malce exteriores amplos, 

 sinistra dextram obvolvente, fornicatge, apice late rotun- 

 data', laino contigua. Mahi interiores ])erminuta>, conies, 

 malis exterioribus contccta?. Palpi minuti, conici, biar- 

 ticulati, malis exterioribus manifesto brcviores. 



Labium anq)lum. Processus mandibulares angusti, acuminati, 

 retro direeti. Lohi intermedii in lobos laterales confusi, 

 amplissimi, fornicati, dextro sinistnmi obvolvente, apice 

 lingulati, mandibulas pra^ter apicem mala3 extcrioris con- 

 tegentes. 



