meget bevegelige og kan tilsammen virke som et 
meget kraftigt tangformigt Griberedskab, 
Af Munddelene er Overleben og de 2- Kind. 
bakker let ioinefaldende. Derimod er de 2 Par Kja- 
ver meget vanskeligere at opdage og lader sig egent- 
lig kun ngiere undersoge ved Dissection. 
Overleben (Tab. VI, Fig. 9, L; Tab. VII, Fig. 
1, L; Fig. 3) har Formen af en aflang Lap, der fra 
Hovedets Ventralside strekker sig bagtil, og sedvan- 
ligvis fuldsteendig dekker over Kindbakkernes Tygge- 
dele (se Tab. VI, Fig. 9). Den viser paa Midten en 
svag Udvidning og ender med en stump Spids, hvis 
Kanter er fint cilierede. Dens ydre Flade er noget 
convex, medens den indadvendte Flade er plan eller 
concav og laadden af fine, tildels gruppevis ordnede 
Haar. “Ved Hjelp af flere sterke Muskler, som fra 
Hovedet passerer igjennem dens Indre, kan den 
snart loftes op fra Kindbakkerne, snart presses ind 
mod dem igjen. Ind under dens Basis ligger (se 
Tab. VII, Fig.3) Mundaabningen i Form af en tver- 
oval Spalte, der bagtil begreendses af en ubetydelig 
fremspringende, haaret Kant. Nogen egentlig Under- 
lebe er derimod ikke tilstede. 
Kindbakkerne (Tab. VI, Fig. 9, M; Tab. VII, 
Fig. 1, M; Fig. 4) er af meget kraftig Bygning og 
omslutter som et Par Boiler den nedre Del af Ho- 
vedet paa Greendsen mellem dets forreste og bagerste 
Parti. Det convexe baadformige Corpus, der saa- 
godtsom fuldstendig udfyldes af de kraftige, indad 
convergerende Tyggemuskler, ender oventil i en 
Spids, der er bevegeligt indleddet til Hovedets Inte- 
gument ved Enden af den dorsale Sutur, der be- 
grendser Nakkesegmentet fortil. Den ventrale Ende, 
eller den egentlige Tyggedel, er (se Tab. VIL, Fig. 4) 
sterkt indboiet og begreendset fra Corpus ved en 
svag Indknibning eller Hals. Den er stumpt afkuttet 
i Enden og har en oval Tyggeflade, der ved sterk 
Forstoerrelse (Fig. 5) viser, sig fint riflet paatveers, 
med den ydre Del af Riflerne noget grovere og besat 
med Rekker af tet sammentrengte tandformige 
Fremspring. Af nogen egentlig skjgwrende Del, er 
der imidlertid intetsomhelst Spor. 
De 2 Par Kjever kommer forst tilsyne, naar 
man betragter Dyret fra Bugsiden, efterat de for- 
reste Branchialfodder er fjernede eller lagte om til 
Siderne (se. Tab. VI, Fig. 9,m’—m*; Tab. VII, Fig. 1, 
m'-—m*). De er begge forholdsvis smaa og af enkel 
Bygning. — Forste Par (Tab. VII, Fig. 6) bestaar 
46 
articulated with the shaft and more or less strongly 
incurved, and gradually diminishes in breadth to- 
wards the point, which is bluntly rounded. In con- 
trast to what is the case in the female, these antenne 
are, in the male, very mobile, and can act together 
as a very powerful forceps-formed prehensile ap- 
paratus. 
Of the oral parts, the upper lip.and the 2 man- 
dibles are readily visible. On the other hand, the 
2 pairs of maxilla are much more difficult to dis- 
cover and can, in reality, only be closely investigated 
upon dissection. ; 
The anterior lip (Pl. VI, fig. 9, L; PI. VII, figs. 
1, L; fig. 3) has the shape of an oblong lobe, which 
extends backwards from the ventral side of the 
head, and usually completely covers over the masti- 
catory parts of the mandibles (see Pl. V1, fig. 9). 
It exhibits at the middle a faint dilation, and ter- 
minates in a blunt point whose edges are finely 
ciliated. Its outer surface is somewhat convex, 
while the inwards turned surface is plane or con- 
cave, and fluffy with fine hairs arranged partly in 
groups. With the aid of several strong muscles 
which from the head pass through its inside, it can 
easily be raised up from the mandibles, and be 
easily again pressed in towards them. In below its 
base lies the oral aperture, in the shape of a trans- 
verse-oval fissure, which is bordered behind by an 
inconsiderably projectant hirsute edge. Any real 
posterior lip is, on the contrary, not present. 
' The mandibles (Pl. VI, fig. 9, M; Pl. VII, fig. 
1, M, fig. 4) are of very powerful structure, and 
enclose, like a pair of bows, the lower part of 
the head at the limit between the anterior and 
posterior portions. The convex cymbiform corpus, 
which is almost completely occupied by the power- — 
ful, inwards-convergent masticatory muscles, ter- 
minates above in a point, which is movably arti- 
culated to the integument of the head, at the ex- 
tremity of the dorsal suture which limits the cer- 
vical segment in front. The ventral extremity, or 
the real masticatory part, is (see Pl. VII, fig. 4) 
strongly incurved and defined from the corpus by 
a faint constrietion or neck. It is bluntly truncated 
at the extremity, and has an oval masticatory sur- 
face which upon powerful magnification (fig. 5) shows 
itself to be finely fluted transversally, with the 
outer part of the flutings somewhat coarser, and 
beset with series of closely crowded dentiform, pro- 
jections. Of any real cutting part there is, how- 
ever, no trace.’ 
The 2 pairs of maxille appear first to view 
when we observe the animal from the ventral side 
after the foremost branchial feet have been removed 
or placed away to the sides (see Pl. VI, fig. 9 m.1W— 
m.?; Pl. VII, fig. 1 m.t—m.*). They are both rela- 
tively small and of simple structure. — The first 
e Am 
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