8o 



Gen. Limnadia, lirosniart. isi^n. 



Slægtscharacteristik. — Skallen sta-rkt saiiiinon- 

 1r\kt. meget tynd, ,i;'lat. uden t\-(lelige rinlidiici-, men 

 Ims ili't V(ixiu'I)\r meil tallage Væxtstrilier. Kove- 

 ilet tdi'liiildsvis lidet dg 1'drsyiiet med et stilket dor- 

 salt Fastheftniiigsovgan, l'anded(d'jn kdiiisk frem- 

 springende dg sondret fra ivostrum vim! en vinkol- 

 forniig [ndlmgtning. Foddinaies Antal dinkring 24 

 Par, den dorsale Laji af I*'\'d|)oditen knn lidet frem- 

 ragende; Epipoditcn forlidldsvis liilen. I lalepladerne 

 ndtndcne nedentil i i't tilspiilset, ikke kldformigt 

 Hjoiaie og rint tandede liagtil. 1 )e sammensatte 

 nine tydeligt adskilte, skjondt ta't sanimenstillede; 

 det enkle i)ie ti'iangnki'rt. h'orste Par Folere for- 

 holdsvis korte, men tydeligt lajipede i sin ydre I)el ; 

 "idet I'ar mecl den indre <!ren Lengere eiul den \-dre, 

 hegge delte i talrige skiveformige Led. besatte i 

 den indre Kant med lange Svonimelioi-ster, i den 

 ydre med korte i'igge. Æ.ggene meget snnia, inn- 

 givne af en turliinfdi'nu't Skal. Forplantningen nde- 

 Inkkende parthendgenetisk. L'd\iklingen en eomplet 

 I^letannirpliose. 



Bemærkninger. — Shegten Limiiadid blev forst 

 opstillet af Jjrogniart allerede i lSi!(), medens Sheg- 

 ten Esthcrid daterer sig fra en langt senere Tid, 

 hvorfor ogsaa Familien boi- lienæ\iK's efter (h'n for- 

 ste og ikke, som det ofte er skeet, efter den sidste 

 Slægt. Fra Shogten Esfherin er nserva-rende Shegt 

 let kjendelig ved den sta'rkere samnienti'vkte og 

 tyndere Skal, paa hvilken ingen tydelige Fniboner 

 tindes, ved Hovedets meget forskjellige l''(n'ni, tildels 

 ogsaa ved Iste 1'ar Foleres, Foddernes og Hale- 

 pladernes Strnetnr. ^[eget na'rmere staar den Sheg- 

 ten EnJiiixtdia 1'aekard, og den eneste nier<' va'sent- 

 lige Forskjel synes at va're, at Arterne af denne 

 sidste Slægt er, ligesoni de af Sl. Esflieria, bis(>xnelle. 

 nnnlens Hanner af Sl. fJiiimi</ia endnn ilcke, trods 

 de diidiyggeligste Ffterforskninger. er fdi'efundm;' dg 

 rimeligvis heller ikke existerer. i\[an kjender hidtil 

 med Sikkerhed knn 2 Arter af denne She.gt, en eiinj- 

 ])aMsk og en amerikansk, L. atiiiricaud Morse. De 

 ovrige til denne Shegt henregnede Arter synes alle 

 at lienhore til den nærstaacnde Shegt, Eiilii)i(idia. 



Limnadia lenticularis (lan) 



i ri. XIV-.VVU;. 

 Monocuhts lent iritla ris. Linné, Fauna Sveoica. ICdit. L'dii p. t'.ifl. 



Daplmia tjigas. Ileriiiiui, .Méni. ai'torol. \<. Kil. Pl. V, lij;. I, .'>, 



Pl. IX, iig. a. 

 Limnadia ITcrmanni, Brouniart, Méni. du Mus. d'liist. nat.. 



Tome VI, ],. Sl, Tl. 1;(. 

 Limnadia gii/as, (irube, .\ifliiv l'. Naturgeschichte, Ifl .lahrg., 



Bd. 1, p. 164. 



Artscharacteristik. — Skallen, seet fra Siden, 

 bredt dval. metl den storste Hoide foran ^Fidten, 



Gen. Limnadia, p.rogniart, is2(i. 



Generic Characters. — Shell greatly eonijjressed, 

 very thin, smooth, without distinct nmbones, Init 

 with numerous lines of growth in the full-grown 

 animal. Head eom])arati\-ely small and furnished 

 with a stalked dorsal atHxing organ: frontal part 

 (■(niieally ])rojecting. and defined from the rostrum 

 by an angular sinus. Xiiinber of feet, altout 24 

 ]>airs; dorsal lo!)e of the exopodite f)nly slightly 

 projeeting; ejiipodite edm]iaratively small. Caudal 

 lamellii' drawn dut below to a sliar|). not elawlike 

 angle, and linely dentated |)osteriorly. ('omjxiund 

 eyes i|uite distinct I'rom one another, though placed 

 close togethiM': oetdlus triangular. First jiair of 

 ! antenna:' eomparativcdv short but distinetlv lohed 

 in tlieir distal |Hirtion; 2nd |>aii- with the inner 

 ramus longer than the outer, and both divided into 

 numerous laminai- joints, chithed on the inner edge 

 with long natatory bristles, on the outer with 

 short spines. ()\a very small, surrcjunded hv a 

 turbinate shell. l'ro|)agatidn exclusively partheno- 

 genetic. Development a complete metamorphosis. 



Remarks. — The genus Linniadia was lirst 

 established by ISrogniart as early as ls20. while 

 the genus Esthcrio dates from a much later time. 

 j The family ought therefore to be named after the 

 I first genus, and not, as is so often done, after the 

 last. The present genus is easily distinguishable 

 from E.<fhcria }>y the greater compression and 

 thinness of its shell, on which no distinct umbones 

 are to be found: b\- the ver\- ditlerent form of the 

 head; and to some extent l)y tiie stiaicture of the 

 1st pair of antenna', the legs, and the caudal lamellæ. 

 The genus Enlimadia, Packard, is far more (dosely 

 allied, and the only essential dill'erence seems to be 

 that the s])ecies of this last genus, liki> thdse of the 

 genus Esthcria, are bisexual, while males of the 

 genus Lim)i((dia. in spite of the most careful investi- 

 gations, have not yet been fdund, and probably do 

 not exi.st. Only two species of this genus are as 

 vet knowti, (Mie Furd|iean and one American, //. 

 ivHcricaua. Morse. The other speides referred io 

 this genus would seem all to belong to the nearly- 

 allied genus, Enliniadia. 



Limnadia lenticularis (Lin.) 



>i'i. \i\-.\\ii . 



Monocidus leHticitlariK, Linnæus, Fauna .Svecioa, Edit, lida, 



p. (99. 

 Daphnia giyas. llerniau, .Mcui. a[iterol. p. l:!l, I'l. V, ligs. 1..'); 



PI. IX, lig. a. 

 Limnadia Jlennanni, Brogniart, Mcni. du Mus. iljnst. nat. 



Tome VI, p. SI, PI. l:!. 

 Limnadia (jigas, Grulie, .Vrcliiv f. Naturgescliichte, 19do Jalirg. 



Bd. I, p. l.-il. 



Specific Characters. — Shell, seen from the 

 side, liroadly nval. with the greatest height in front 



