68 



Detainer, kan det være et Sporgsinaal. om (lii5se 2 

 Slægter i Virkelig-liedeii altid lader sig holde skarpt 

 ud fra hiiianden. Man vil nemlig Unde, at Enditer- 

 nes Længde jma Iste Fodpar er hos Arterne af 

 Slægten Lcpidiiyns ikke lidet varierende, og Hale- 

 pladen er ialfald hos enkelte Arter saa betydelig 

 rednceret i Storrelse, at den næsten maa kaldes 

 rudimentær. Rygskj eldet er vistnok ialmindelighed 

 storre hos Lepidiints end lios A2»(s, og dækker der- 

 for hos den forste Slægt en storre Del af Kroppen 

 end lios den sidste; men man vil dog tinde, at der 

 ogsaa i saa Henseende er adskillig Variation hos 

 Arterne af begge Slægter. Hos Lephhniis r/Jac/aJis 

 er det saaledes neppe synderligt storre end hos 

 Apus cnncriformis, og hos den nordamerikanske Le- 

 pidurus hilohatus er en fuldkommen ligesaa stor Del 

 af Kroppen nbedækket af Eygskjoldet som lios J_7«(.'; 

 cancriformis. Man kjender (> eller 7 forskjellige 

 Ai'ter af denne Slægt, hvoraf knn en tilliorei' Nor- 

 ges Fauna. 



Lepidurus glacialis (Ki 



liver 



a'). XI. -XII, XIII). 



Ajjus (jlndalh, Kroyi-r, Nat. Tiilsskr. 2 R. Bd. 2, ]i. 481. 



LepidHrns (jlacialis, Packard, Monogr. Phyll. Crust. North Ame- 

 rica. U. St. Geol. Surv. I, p. 316. PL XVI, Pl. XVII, ligs. 

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



Artscharacter. — Eygskjoldet af middelmaadig 

 Storrelse. bredt ovalt, jevnt ufrundet fortil. med en 

 tydeligt markeret dorsal Kjol: det bagre Indsnit 

 temmelig dybt, vinkelformigt. 12 — 18 Segmenter ube- 

 dækkede liag Rvgskjoldet. Halepladen forlioldsvis 

 meget kort, i Regelen ikke længere end sidste Hale- 

 segment er bredt, tungeformig, neppe ind.snoret ved 

 Basis, undertiden svagt indskaaret i Spidsen, Kanterne 

 med et begrændset 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 Spiritusexem])larer ensformig gron. Læng- 

 den af Hunnen indtil 24 mm, a t' Hannen neppe mere 

 end 12 mm. 



Bemærkninger. — Nærværende Art er forst 

 kortelig be.><kreven paa ovenanførte Sted af Krøyer, 

 og senere afbildet af samme Forfatter i (laimard's 

 store Reiseværk, dog her uden nogen Beskrivelse. 

 Den adskiller sig fra de ovrige Arter af Slægten, 

 og navnlig fra den i Mellemeuropa alraindeligt fore- 

 kommende Lepidariis produchis, ved Rygskjoldets 

 ringere Storrelse, de meget korte Enditer paa Iste 

 Fodpar, og ved Halepladmis Ivortlied. 



respects exactly with those oi Aptts; both in external 

 habitus and in anatomical details, it may be questioned 

 whether these two genera can in realit}^ always be 

 kept distinct from one another. For instance, it 

 Avill be found that the length of the endites in the 

 first ])air 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 tliis respect there is considerable 

 variation in the species of both genera. For instance, 

 iwl-jvpidurus (/iacialis it h scarcely larger than in Ajms 

 cancriformis. and in the North American I^epidurus 

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

 uncovered by the carapace as in Ajjus cancriformis. 

 Six or seven different species of this genus are 

 known, only one of which belongs to tlie fauna of 

 Norway. 



Lepidurus glacialis (Kroyer) 



(PI. XI, XII, Xlllj. 



Apus (jlnci(ili.'<. Kroyer, Nat. Tidsskr, 2 R., Bd. 2. p. 431. 



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

 rica. V. St. Geol. Surv. I, p. 316, I'l. XVI, PI. .XVII, figs. 

 1—5, PI XXI, figs. 1, 2. 



Specific Characters. — Carapace of medium size, 

 broadly oval, evenly rounded in front, with a dis- 

 tinctly-marked dorsal keel ; ])osterior emargination 

 rather deep and angular. From 12 to 18 of the 

 posterior segments not covered by the carapace. 

 Caudal lamella comjjaratively very short, generally 

 not longer tlian tlie Itreadth 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 lieyond ' 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. — Tlie present species was first briefiy 

 described in the above-named paper, by Kroyer, and 

 subsequently figured li\- tlie same author in Gai- 

 mard's great Avork, but without any descriptitni. It 

 difiers from the other species of the genus, and 

 especially from Lepidurus producfus, so common in 

 Centi'al Europe, by the smaller size of the carapace, 

 the A'ery short endites of the first pair of legs, and 

 the shortness of the caudal lamella. 



