Detailler, kan det vere et Sporgsmaal, om disse 2 
Slegter i Virkeligheden altid lader sig holde skarpt 
ud fra hinanden. Man vil nemlig finde, at Enditer- 
nes Lengde paa 1ste Fodpar er hos Arterne af 
Slegten Lepidurus ikke lidet varierende, og Hale- 
pladen er ialfald hos enkelte Arter saa betydelig 
reduceret i Storrelse, at den nesten maa kaldes 
rudimenter. Rygskjoldet er vistnok ialmindelighed 
storre hos Lepidurus end hos Apus, og dekker der- 
for hos den forste Slegt en storre Del af Kroppen 
end hos den sidste; men man vil dog finde, at der 
ogsaa i saa Henseende er adskillig Variation hos 
Arterne af begge Slegter. Hos Lepidurus glacialis 
er det saaledes neppe synderligt storre end hos 
Apus cancriformis, og hos den nordamerikanske Le- 
pidurus bilobatus er en fuldkommen ligesaa stor Del 
af Kroppen ubedekket af Rygskjoldet som hos Apus 
cancriformis. Man kjender 6 eller 7 forskjellige 
Arter af denne Slegt, hvoraf kun en tilhorer Nor- 
ges Fauna. 
Lepidurus glacialis (Kroyer). 
(Pl. XI; XII,. XI). 
Apus glacialis, Kroyer, Nat. Tidsskr. 2 R. Bd. 2, p, 481. 
Lepidurus glacialis, Packard, Monogr. Phyll. Crust. North Ame- 
rica. U. St. Geol. Surv. I, p. 316, Pl. XVI, Pl. XVII, figs. 
1—5, Pl. XXI, figs. 1, 2. 
Artscharacter. — Rygskjoldet af middelmaadig 
Storrelse, bredt ovalt, jevnt afrundet fortil, med en 
tydeligt markeret dorsal Kjol; det bagre Indsnit 
temmelig dybt, vinkelformigt. 12—18 Segmenter ube- 
dekkede bag Rygskjoldet. Halepladen forholdsvis 
meget kort, i Regelen ikke leengere end sidste Hale- 
segment er bredt, tungeformig, neppe indsnoret ved 
Basis, undertiden svagt indskaaret i Spidsen, Kanterne 
med et begreendset Antal Sagtakker. 2det Par Fo- 
lere tilstede som smaa Rudimenter. iste Fodpar 
med Enditerne meget korte, kun ubetydeligt over- 
ragende Kanterne af Rygskjoldet. Farven hos le- 
vende Exemplarer mere eller mindre mork oliven- 
brun, paa Spiritusexemplarer ensformig gron. Leeng- 
den af Hunnen indtil 24 mm, af Hannen neppe mere 
end 12 mm. 
Bemerkninger. — Nerverende Art er forst 
kortelig beskreven paa ovenanforte Sted af Kroyer, 
og senere afbildet af samme Forfatter i Gaimard’s 
store Reiseveerk, dog her uden nogen Beskrivelse. 
Den adskiller sig fra de ovrige Arter af Slegten, 
og navnlig fra den i Mellemeuropa almindeligt fore- 
kommende Lepidurus productus, ved Rygskjoldets 
ringere Storrelse, de meget korte Enditer paa Lste 
Fodpar, og ved Halepladens Korthed. 
68 
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respects exactly with those of Apus, both in external 
habitus and in anatomical details, it may be questioned 
whether these two genera can in reality always be 
kept distinct from one another. For instance, it 
will be found that the length of the endites in the 
first pair of legs in the genus Lepidurus, varies not 
a little; and the caudal lamella, at any rate in cer- 
tain species, is so greatly reduced’ in size as to be 
almost rudimentary. The carapace is certainly ge- 
nerally larger in Lepidwrus than in Apus, and there- 
fore covers, in the former genus, a larger part of 
the body than in the latter; but it will still be 
found that even in this respect there is considerable 
variation in the species of both genera. For instance, 
in Lepidurus glacialis it is scarcely larger than in Apus 
cancriformis, and in the North American Lepidurus 
bilobatus, fully as large a part of the body is left 
uncovered by the carapace as in Apus cancriformis. 
Six or seven different species of this genus are 
known, only one of which belongs to the fauna of 
Norway. 
Lepidurus glacialis (Kroyer). 
(Pl. XI, XII, XII). 
Apus glacialis, Kroyer, Nat. Tidsskr. 2 R., Bd. 2, p. 481. 
Lepidurus glacialis, Packard, Monogr. Phyl]. Crust. North Ame- 
rica. U.St. Geol. Surv. I, p. 316, Pl. XVI, Pl. XVII, figs. 
1—5, Pl. XXI, figs. 1, 2. 
Specific Characters. — Carapace of medium size, 
broadly oval, evenly rounded in front, with a dis- 
tinctly-marked dorsal keel; posterior emargination 
rather deep and angular. From 12 .to 18 of the 
posterior segments not covered by the carapace. 
Caudal lamella comparatively very short, generally 
not longer than the breadth of the last caudal seg- 
ment, linguiform, scarcely constricted at the base, 
and sometimes slightly notched at the extremity: 
edges with a limited number of denticles. Second 
pair of antenne present as small rudiments. First 
pair of legs with the endites very short, projecting 
only slightly beyond the edges of the carapace. 
Colour in living specimens more or less dark olive 
brown, in spirit specimens, uniform green. Length 
of the female up to 24 mm., of the male, scarcely 
more than 12 mm. 
Remarks. — The present species was first briefly 
described in the above-named paper, by Kroyer, and 
subsequently figured by the same author in Gai- 
mard’s great work, but without any description. It 
differs from the other species of the genus, and 
especially from Lepidurus productus, so common in 
Central Europe, by the smaller size of the carapace, 
the very short endites of the first pair of legs, and 
the shortness of the caudal Jamella. — 
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