acta 
Rygkanten hos fuldvoxne Individer sterkt buet i 
sin forreste Del, Bugkanten jevnt convex, Forenden 
meget kort, afstumpet, Bagenden noget uddraget og 
smalt tilrundet, med en tydelig Vinkel oventil —: 
seet ovenfra smalt tenformig, bredest foran Midten. 
Veextstriberne ikke meget skarpt markerede, og vex- 
lende efter Alderen indtil 15 paa hverSide. Hovedet 
nesten af trianguler Form, med Pandedelen smalt 
konisk og skilt fra det triangulere Rostrum ved et 
dybt vinklet Indsnit. Foddernes Antal hos fuld- 
voxne Individer 24 Par, 9—1lte Par med Exopo- 
ditens dorsale Lap traadformigt forlenget. Hale- 
pladerne hver med 10—16 smaa Tagger ovenfor det 
tornformigt udtrukne nedre Hjorne; Haleklorne fint 
tandede langs den concave Kant og besatte med 
fine Borster i den basale Del. Farven mere eller 
mindre tydelig olivengron, Fodderne ialmindelighed 
lyst gulrede. Leengden af Skallen indtil 17 mm. 
Bemerkninger. — Allerede Herman har ytret 
den Formodning, at det af ham som Daphnia gigas 
beskrevne Dyr maaske kunde vere identisk med 
Linné’s Monoculus lenticularis, og ogsaa Grube *) 
synes at vere af samme Mening. De senere af 
Prof. Lilljeborg*) anforte Data synes endmere at 
bekreefte Rigtigheden af denne Anskuelse, og det 
forekommer mig derfor nu at vere fuldt berettiget 
at optage igjen den Linnéiske Artsbetegnelse, lenti- 
cularis, saameget mere som den er noksaa beteg- 
nende. Det Navn, hvorunder nerverende Form af 
de fleste Forfattere, ogsaa af Prof. Lilljeborg, er op- 
fort, er Limnadia gigas. 
Beskrivelse. 
Hos de storste af mig observerede Exemplarer 
har Skallen en Lengde af 12 mm. og en Hoide af 
9mm. Prof. Lilljeborg har fundet den at kunne 
naa en Lengde af indtil 17 mm. og en Hoide af 
ner 13 mm. Men en saadan Storrelse synes dog at 
maatte ansees som exceptionel. 
Skallen, der fuldsteendigt omslutter Dyret, saa 
at kun den forreste Del af Hovedet med Aarerne 
og Halen kan strekkes udenfor samme, er sterkt 
sammentrykt fra Siderne og temmelig tynd og gijen- 
nemsigtig, hvorfor Legemet sees meget tydeligt 
igjennem samme (se Tab. XI, Fig. 1). Den bestaar 
af 2 symetriske Halvdele eller Valvler, der langs 
Dorsalsiden steder sammen under en spids Vinkel 
og her er fast forbundne med hinanden, uden nogen 
virkelig Laas. Da imidlertid Skallen er meget 
elastisk, er Valvlerne til en vis Grad bevegelige 
1) Ueber die Gattungen Estheria und Limnadia, p. 68. 
*) Ofversigt af Kgl. Vet. Akad. Forhandl. 1871, p. 824. 
of the middle; dorsal margin, in full-grown speci- 
mens, much arched in the foremost part; ventral 
margin evenly curved, anterior extremity very short 
and blunt, posterior end rather elongated and nar- 
rowly rounded, with a well-marked angle above —: 
seen from above narrowly fusiform, with the greatest 
breadth in front of the middle. Lines of growth 
not very clearly marked, varying according to age 
up to 15 on each side. Head almost triangular, 
with the frontal part narrowly conical and sepa- 
rated from the triangular rostrum by a deep an- 
gular notch. The number of legs in full-grown 
specimens 24 pairs, the 9th to the 11th pairs having the 
dorsal lobe of the exopodites elongated in the form 
of filaments. Caudal lamelle each with from 10 to 
16 small denticles above the spine-like, elongated 
lower corner; caudal claws finely dentated along 
their concave edge, and the basal part clothed with 
fine bristles. Colour more or less distinctly olive- 
green, legs generally light yellowish red. Length 
of shell up to 17 mm. 
Remarks. — Herman has already surmised that 
the animal described by him as Daphnia gigas may © 
perhaps be identical with Linneeus’s Monoculus lenti- 
cularis, and Grube') seems to be of the same opi- 
nion. The data subsequently furnished by Prof. 
Lilljeborg*) seem still further to confirm the cor- 
rectness of this view, and I therefore feel fully 
justified in adopting again the Linnean specific de- 
signation, lenticularis, the more so as it is fairly 
characteristic. The name by which the present 
form is specified by most authors, Prof. Lilljeborg 
included, is Limnadia gigas. 
Description. 
In the largest specimens examined by me, the 
shell has a length of 12 mm. and a height of 9 mm. 
Prof. Lilljeborg has found it attaining a length of 
17 mm., and a height of nearly 13 mm.; but such a 
size must probably be considered exceptional. 
The shell, which completely envelopes the ani- 
mal, so that only the anterior part of the head, 
with the oars and the tail can be extended from 
it, is greatly compressed, and rather thin and tran- 
sparent, so that the body is distinctly seen through 
it (see Pl. XIV, fig. 1). It consists of 2 symmetrical 
halves or valves which meet at an acute angle 
along the dorsal side, and are there firmly united 
to one another, without any true hinge. As, how- 
ever, the shell is very elastic, the valves are mov- 
able to a certain extent, and can be opened a little, 
1) Ueber die Gattungen Estheria und Limnadia, p. 68. 
*) Ofversigt af Kgl. Vet. Akad. Forhandl. 1871, p. 824. 
eS ee re, eee ee 
