36 
de ogsaa her paa samme Maade. Forskjellen er 
altsaa, at her alle bag Munddelene folgende Lemmer 
er wgte Branchialfedder, medens dette hos Phyllo- 
cariderne kun er Tilfeeldet med en Del af dem. 
I Folernes Bygning er der saa stor Forskjel hos de 
forskjellige Former, at intet andet bestemt feelles 
Charactertrek kan anfores end, at det iste Par ude- 
lukkende er sensitive og derfor af en meget tander 
Structur.. Ogsaa Minenes Bygning er meget forskjel- 
lig, idet de snart er stilkede som hos Phyllocariderne, 
snart sessile, snart sammensmeltede til et enkelt i 
det indre af Hovedet beliggende Organ. Characte- 
ristisk ligeoverfor Phyllocariderne er Tilstedeverel- 
sen af et mediant Enkeltoie (ocellus). Angaaende 
Munddelenes Structur, kan fremheves Mangelen af 
Palper paa Kindbakkerne, og den forholdsvis simple 
Bygning af de 2 Par Kjever. 
De hidtil bekjendte Phyllopoder vil passende 
,kunne fordeles paa 3 storre Afdelinger, for hvilke 
jeg allerede i 18677’) har foreslaaet folgende Benzev- 
nelser: Anostraca, Notostraca og Conchostraca. For- 
skjellen mellem disse Afdelinger er saa stor og gjen- 
nemgribende, at de ikke, som af de fleste Forskere 
gjort, kan opfattes som blotte Familier, men. ube- 
tinget bor tillegges en langt hoiere systematisk 
Verdi (Tribus eller Sectioner). Til enhver af disse 
Grupper horer et meget begrendset Antal af Sleg- 
ter, som delvis lader sig fordele paa flere Familier. 
De herhen horende Slegttypers Faatallighed 
og i Regelen overordentlig skarpt udpreegede For- 
skjel, i Forbindelse med deres sporadiske Forekomst 
paa vidt adskilte Localiteter, synes at tyde hen paa, 
at vi i Phyllopoderne har. de sidste divergerende 
Grene af en uddsende Dyrgruppe, som rimeligvis, 
at domme efter flere paleontologiske Fund, har veret 
langt rigere representeret i tidligere Jordperioder. 
Ogsaa af disse Dyrs Organisation og Udvikling synes 
man at vere berettiget til at slutte, at de maa vere 
af meget gammel Oprindelse. Det yderlig variable 
Antal af Kropssegmenter og af Lemmer, disse sid- 
stes uniforme Bygning, den oftest kun .lidet skarpt 
udpregede Sondring af Legemet i tydeligt begrend- 
sede Kropsafsnit, alt dette er Characterer, der aaben- 
bart henpeger paa primitive Tilstande, hvori endnu 
ikke de hos de moderne Crustacegrupper gjeldende 
Forhold rigtigt har fixeret sig. Phyllopoderne min- 
der i denne Henseende ikke saa lidet om de #ld- 
gamle Trilobiter, ligesom der ialfald hos Afdelingen 
Notostraca er en umiskjendelig habituel Lighed med 
de ligeledes langt op i den geologiske Tid gaaende 
') G. O. Sars, Histoire naturelle des Crustacés d’eau douce 
de Norvége, I. 
respiratory, they are also named here in the same 
manner. The difference, therefore, is, that here all 
the appendages placed behind the oral parts are 
real branchial feet, while in the Phyllocarida that 
is only the case with a part of them. ‘In the 
structure of the antenne there is such a great differ- 
ence in the various forms, that no other certain 
characteristic feature in common can be given, than 
that the Ist pair are exclusively sensitory and there- 
fore of a very delicate structure. The structure of 
the eyes also is very different, as they are some- 
times pedunculated, as in the Phyllocarida, sometimes 
sessile, sometimes coalescent to a single-organ situ- 
ated in the interior of the head. The presence of 
a single median eye (ocellus) is a characteristic 
feature in contrast with the Phyllocarida. Re- 
garding the structure of the oral parts may be 
mentioned, the absence of palpi on the mandibles, 
and the relatively simple structure of the 2 pairs 
of maxille. 
The Phyllopods hitherto known may suitably be 
assigned to 3 large divisions, for which the author, as 
early as 18671), proposed the following designations: 
Anostraca, Notostraca and Conchostraca. The differ- 
ence between those divisions is throughout, so great, 
that they cannot be regarded as families only, as 
has been done by most writers, but ought, evid- 
ently, to be assigned a far higher systematic value 
(Tribus or Sections). To each of these groups 
there pertain a very limited number of genera, 
which to some extent may be referred to several 
families. 
The paucity in number of the generic types 
pertaining hereto, and the, as a rule, extraordinarily 
sharply distinguished difference, in connection with 
their sporadic occurrenée in widely separated loca- 
lities, seems to give an indication that in the Phyllo- 
pods we have the last diverging branches of a van- 
ishing animal group, which, probably, judging by 
several paleontological discoveries, has been far 
more abundantly represented in earlier periods of our 
earth’s history. From the organisation and develop- 
ment, also, of these animals, it seems as if we were 
warranted in concluding that they must be of very 
old origin. The extremely variable number of body 
segments and of appendages; the uniform structure 
of the last-named; the usually only little sharply 
distinguished separation of the body in distinctly 
defined divisions, are all characteristics that evid- 
ently point to primitive conditions, in which the 
regulating relations of the modern groups of cru- 
staceans had not yet been thoroughly consolidated. 
The Phyllopods remind us in that respect, not so 
little of the ancient Trilobites, while, also, there, in 
') G. O. Sars, Histoire naturelle des Crustacés d’eau douce 
de Norvége, I. 
