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triangulære, skarpt begrændsede Lapper, der forestiller
Øien-loberne. Lige bag disse danner Hovedskjoldet nedad til
liver Side en dyb 1 drandning. indenfor hvilken
Kindbakkerne og Overlæben træder frit frem (se Fig. 3), medens
v det længere bagtil bøier sig om paa Bugfladen i Form af
2 uregelmæssigt firkantede Flige, der mellem sig indslutter
de ovrige Munddele. Disse Flige dækker sammen med
Hovedskjoldets bagre Sidedele til hver Side en tydelig Hule,
hvori 2 eiendommeligt modificerede Vedhæng til Munddelene
rager frem. Det bagerste og største af disse Vedhæng danner,
som nedenfor nærmere skal vises, et compliceret
Ventilapparat, ved hvis Bevægelser en stadig Strømning af
Vandet i Retningen bagfra fortil underholdes i de nævnte Huler.
Indgangsaabningerne til disse Huler er beliggende ved Basis
af Kjævefødderne, medens Udgangsaabningerne ligger foran
de omtalte Flige, mellem disse og Kindbakkernes Corpora.
Det hel" er. saaledes som af Fritz Midler hos Slægten
Tanais paavist, utvivlsomt at betragte som et
Respirations-apparat og har sit fuldstændige Homologon i Cumaceernes
Gjellehuller. skjøndt paa langt nær ikke opnaaende disses
mægtige Udvikling. Lige bag Kjævefødderne sees paa
Bugsiden en ganske smal transversal Chitinplade, der aabenbart
forestiller Sternaldelen af det forøvrigt ganske med Hovedet
sammen voxede lst fodbærende Segment. Til Siderne af
denne Chitinplade og umiddelbart indenfor en kort fra
Hovedskjoldet udskydende tungeformig Fortsats er
Saxfødderne fæstede.
Af tydeligt begrændsede Forkropssegmenter budes
ligesom hos de øvrige til denne Gruppe hørende Former kun
li, idet det lste fodbærende Segment, som anført,
saagodtsom ganske er gaaet op i Dannelsen af Hovedskjoldet. Det
lste af disse frie Segmenter er meget fast og, som det
synes, ubevægeligt forbundet med Hovedsegmentet. I let er
noget bredere end dette, med jevnt afrundede Sidedele, og
er bagtil stærkt udrandet til Optagelse af den smale forreste
Del af 2det Segment. Dette og de følgende Segmenter er
betydelig smalere og ved dybe Indsnøringer skilte fra
hinanden. De har alle (se Fig. 2) meget smaa. med de
tilsvarende Lemmer forbundne og fra selve Segmenterne skarpt
adskilte Epimerer. De til lste Segment hørende er størst,
men ikke som hos Slægten Apseudes forlænget til
fortilrettede Torner.
Bagkroppen, der indtager omtrent l/1 af Totallængden,
bestaar af (i tydeligt begrændsede Segmenter, hvoraf de 5
forreste er ganske korte og i høi Grad udmærkede ved de
triangulært tilspidsede og til Siderne udstaaende Epimerer.
der giver denne Kropsdel et eiendommeligt saugtakket
Udseende. Sidste Segment er i Enden stumpt afrundet og
noget længere end de 2 foregaaende tilsammen.
Egentlige Øine mangler ganske. Thi indenfor de smaa
occupying the lateral corners of the cephalic shield, are seen
2 triangular, sharply defined lobules, representing the ocular
lobes. Immediately posterior to these lobules, the cephalic
shield forms below, on either side, a deep emarginntion, within
which the mandibles and the labrum are seen freely
protending (fig. 3), while, farther behind, it bends round the ventral
surface in the form of 2 irregular-quadrate lappets, enclosing
the rest of the oral appendages. These lappets, along with
the posterior lateral portions of the cephalic shield, cover,
on either side, a conspicuous cavity, into which 2 peculiarly
modified appendices of the oral parts are observed to
project. The larger and more posteriorly placed of these
appendices, constitutes, as will be shown in the sequel,
a complicated ventilatory apparatus, by the movements of
which an uninterrupted current of water is made to flow
in a postero-antero direction through the aforesaid cavities.
The entrance-apertures to these cavities are located at the
base of the maxillipeds. whereas the outlet-apertures occur
anterior to the above-mentioned lobules, — viz. between the
latter and the corpora of the mandibles. The whole
arrangement must, as shown by Fritz Midler to be the case
in the genus Tanais, unquestionably perform the functions
of a respiratory apparatus, and has its perfect analogue in
the branchial cavities of the Cumacea. though far from
attaining their prodigous development. Immediately posterior
to the maxillipeds are seen on the ventral side an
exceedingly narrow, transversal, chitinous plate, manifestly
representing the sternal portion of the 1st pedigerous segment,
which, for the rest, is quite connate with the bead. On
the sides of this chitinous plate, and immediately anterior
to a short, linguiform projection jutting out from the cephalic
shield, are attached the chelipeds.
Of well-defined thoracic segments, occur, as in the
other forms belonging to this group, 6 only, the first
pedigerous segment being, as stated above, almost entirely
confounded with the cephalic shield. The 1st of these free
segments is exceedingly firm. and. it would appear,
immovably connected with the cephalic segment. It is somewhat
broader than the latter, with uniformly rounded lateral
parts, and has posteriorly a deep emargination. to receive the
narrow foremost part of the 2nd segment. This and the
succeeding segments are considerably narrower, and separated
by deep instrictions from one another. They have all of tbem
(see fig. 2) exceedingly small epimera, connected with the
corresponding appendages and distinctly separated from the
segments themselves. Those on the lst segment are largest,
but not, as in the genus Apseudes, produced to anteriorly
directed spines.
The posterior division of the body, measuring about
one-fourth of the total length, consists of G well-defined
segments, of which the 5 foremost are quite short. a.nd
conspicuously distinguished by the epimera. triangularly
pointed and projecting toward the sides, which gives to this
part of the body a characteristic serrate appearance. The
terminal segment is. at the extremity, obtusely rounded, and
somewhat longer than the 2 preceding ones, taken together.
Eyes, in a strict sense, are entirely wanting. For.
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