68 



Detainer, kan det være et Spørgsmaal, om disse 2 

 Slægter i Vii-keligheden altid lader sig holde skarpt 

 ud fra hiuanden. Man vil nemlig finde, at Enditer- 

 nes Længde paa Iste Fodpar er hos Arterne af 

 Slægten Lepidnriis ikke lidet varierende, og Hale- 

 pladen er ialfald hos enkelte Arter saa betydelig 

 reduceret i Størrelse, at den næsten maa kaldes 

 rudimentær. Eygskjoldet er vistnok ialmindelighed 

 storre hos LepUUrus end hos Apns, og dækker der- 

 for hos den forste Slægt en større 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 Slægter. Hos Lqmlurus glacialis 

 er det saaledes neppe synderligt storre end hos 

 Apus cancriformis, og hos den nordamerikanske Le- 

 pidurus hilobatiis er en fuldkommen ligesaa stor Del 

 af Kroppen iibedækket af Ryg.skjoldet som hos Ajms 

 cancriformis. Man kj ender 6 eller 7 forskjellige 

 Arter af denne Slægt, hvoraf kun en tilkorer Xor- 



ges Fauna. 



Lepidurus glacialis (Kroyer) 



(Pl. XI, XII, XIII). 



Apus glacialis, Kroj'er, Nat. Tidsskr. 2 E. Bd. 2, p. 481. 



Lepidur us glacialis, Packard, Monogr.Phyll. Crust. North Ame- 

 rica. TJ. St. Geol. Surv. 1, p. 316, Pl. XVI, Pl. XVII, figs. 

 1-5, Pl. XXI, figs. 1, 2. 



Artscharacter. — Rygskjoldet af middelraaadig 

 Størrelse, bredt ovalt, jevnt afrundet fortil,, med en 

 tydeligt marker et dorsal Kjol; det bagre Indsnit 

 temmelig dybt, vinkelformigt. 12 — 18 Segmenter ube- 

 dækkede bag E-ygskjoldet. Halepladen forholdsvis 

 meget kort, i Regelen ikke længere end sidste Hale- 

 segment er bredt, tiingeformig, neppe indsnoret ved 

 Basis, undertiden svagt indskaaret i Spidsen, Kanterne 

 med et begrændset Antal Sagtakker. 2det Par Fø- 

 lere tilstede som smaa Rudimenter. Iste Fodpar 

 med Enditerne meget korte, kun \ibetydeligt over- 

 ragende Kanterne af Rj^gskjohlet. Farven hos le- 

 vende Exemplarer mere eller mindre mørk oliven- 

 brun, paa Sjnritusexemplarer ensformig grøn. Læng- 

 den af Hunnen indtil 24 mm, a f Hannen neppe mere 

 end 12 mm. 



Bemærkninger. — Nærværende Art er forst 

 kortelig beskreven paa ovenanførte Sted af Krøyer, 

 og senere afbildet af samme Forfatter i Gaimard's 

 store Reiseværk, dog her uden nogen Be.skrivelse. 

 Den adskiller sig fra de øvrige Arter af Slægten, 

 og navnlig fra den i Mellemeuropa almindeligt fore- 

 kommende Lepidurus producfus, ved Rygskjoldets 

 ringere Størrelse, de meget korte Enditer paa Iste 

 Fodpar, og ved Halepladens Korthed. 



respects exactly with those of Apus, botli in external 

 habitus and in anatomical details, it maj' be i:|uestioned 

 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 Lepidurus 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 Ijipidurus glacialis it is scarcely larger than iwApus 

 cancriformis. and in the North American Lepidurus 

 hilobafus, fully as large a part of the body is left 

 uncovered by the carapace as in Ajyus cancriformis. 

 Six or seven different .species of this genus are 

 known, only one of which belongs to the fauna of 

 Norway. 



I 



Lepidurus glacialis (Kroyer). 



(PI. XI, XII, XIIIj. 



Apus glacialis. Krøyer, Nat. Tidsskr. 2 R., Bd. 2, p. 431. 



Lepidurus glacialis, Packard, Monogr. Phyll. Crust. North Ame- 

 rica. U. St. Geol. Surv. I, p. 316, PI. XVI, PI. XVII, figs. 

 1-6, PI. 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 comparativeh' very sliort, 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 antennæ present as small rudiments. Fir.st 

 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 produchis, 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 lamella. 



