66 
sjeldent lykkes at faa begge i Sammenheeng con- | region, that it is often possible to preserve both 
serveret paa Spiritus. 
Udbredning. — Arten blev forst opdaget af 
Middendorff i Smaatjern paa den sibiriske «Tundra» 
ved Floderne Taimyr og Boganida, ligesom ogsaa i 
Russisk Lapland ved Tri-Ostrowa, og er senere af 
Fries gjenfunden i Ostfinmarken. Derimod er den 
ikke kjendt hverken fra Gronland, det arktiske 
Amerika eller Spitsbergen. 
Sectio II. Notostraca. 
(Skjolddekte Phyllopoder). 
Syn: Phyllopoda cancriformia. 
Character. — Legemet mere eller mindre dek- 
ket oventil af et bredt hvelvet Rygskjold, -der for- 
til er sammenvoxet med Hovedet. Kroppen ensfor- 
migt segmenteret, jevnt afsmalnende bagtil, og en- 
dende med 2 forlengede Haletraade. Qinene ses- 
sile, ner sammen paa Oversiden af Hovedet. Andet 
Par Folere hos det voxne Dyr rudimentere eller 
ganske manglende. Munddelene tet sammentrengte 
bag Hovedets ventrale Duplicatur, og bestaaende af 
Over- og Underlebe, Mandibler og 2 Par Kjever. 
Fodderne overordentlig talrige og tet sammen- 
trengte bagtil, saa at flere Par er feestede til hvert 
enkelt Segment. Ingen ydre Aigbeholder. Udvik- 
lingen en compliceret Metamorphose begyndende med 
et Naupliusstudium. 
Bemerkninger. — Nerverende Gruppe adskiller 
sig meget skarpt fra de ovrige Phyllopoder ved en 
Rekke vel markerede Characterer, hvoraf den mest 
ioinefaldende er det fladt hvelvede Rygskjold, der 
fortil gaar i et med Hovedet og giver Dyret en 
umiskjendelig Lighed med Xiphoswrerne og derigjen- 
nem ogsaa med de forverdenske Trilobiter. Med 
disse sidste stemmer ogsaa nerverende Gruppe 
overens ved det overordentlig store Antal af uni- 
forme Segmenter, hvori Legemet er delt. Idethele 
synes flere Characterer, der udmerkede nogle af de 
eldste forverdenske Crustaceer, tydeligere at afspeile 
sig i neerveerende Gruppe end i nogen af de ovrige. 
Den indeholder for Tiden kun en enkelt Familie. 
together in spirit. 
Distribution. — This species was first disco- 
vered by Middendorff in small lakes on the Siberian 
«Tundra» at the rivers Taimur and Boganida, and 
also in Russian Lapland at Tri-Ostrowa; it was 
subsequently found again by Fries in East Finmark. 
It has not, however, been heard of either from 
Greenland, arctic America or Spitzbergen. 
Section I]. Notostraca. 
(Shield-bearing Phyllopods). 
Syn: Phyllopoda cancriformia, ‘ 
Characters. — Body more or less covered above 
by a broad, vaulted carapace, which is united ante- 
riorly with the head. Trunk uniformly segmented, - 
tapering evenly posteriorly, and ending in two 
elongated caudal filaments. Eyes sessile and close 
together on the upper surface of the head. Second 
pair of antenne in the full-grown animal either ru- 
dimentary or altogether wanting. Oral parts closely 
crowded behind the ventral duplicature of the head, 
and consisting of upper and lower lip, mandibles 
and 2 pairs of maxille. Legs extremely numerous 
and closely crowded together posteriorly, so that 
several pairs are attached to each segment. No 
external marsupium. Development, a complicated 
metamorphosis, commencing with a nauplius stadium. 
Remarks. — The present group is sharply de- 
fined from other Phyllopoda by a series of well-marked 
characters, of which the most conspicuous is the 
vaulted carapace which is united with the head, 
giving the animal an unmistakable likeness to the 
Xiphosure, and thereby also to the paleozoie Trilo- 
bites. With the latter the present group also agrees, 
in the extraordinarily large number of uniform seg- 
ments into which the body is divided. Taken as a 
whole, several of the characters that distinguished 
some of the oldest paleozoic Crustacea, seem to be 
reflected more clearly in the present group than in 
any of the others. 
single family. 
At present, it contains only a 
