~ 
M.T. Thorell on the Systematic Position of the Argulide. 285 
fining strictly the limits of the Branchiopoda among the other 
lower Crustaceans—the compound eyes with unfacetted cornea, 
the absence of palpi or branchial appendages on the oral organs, 
lobed or cloven respiratory or swimming-feet without median 
plates, distinct sexes—occur in the Argulide. The discrepancies 
which depend on their parasitic habits cannot be put forward as 
reasons for the isolated position of the Argulide, at least as long 
as parasitic and free Copepoda are unanimously referred to the 
same order. If we look at these differences, we find that be- 
tween the Argulide on the one side, and the Phyllopoda and 
Cladocera on the other, no greater dissimilarities exist than 
those which separate these two groups from each other. Al- 
though indeed it must be admitted that the Argulide stand 
nearer to the Phyllopoda than to the Cladocera, it seems to us 
nevertheless that the differences we have mentioned (we would 
recall in particular the form and function of the tail, and the 
presence of receptacula seminis), in conjunction with the cha- 
racters which are correlative to their parasitic nature, are suf- 
ficiently strong to set aside the notion of the introduction of 
the Argulidae among the Phyllopoda. We regard them con- 
sequently as a group of the same systematic value as these and 
the Cladocera—that is to say, a suborder, on a par with these, in 
the order of the Branchiopoda,—and propose, since Argulide or 
Argulinad are only suitable as family names, foy this suborder the 
appellation Branchiura, drawn from the characteristic condition 
of the tail in these animals. Just as the Cladocera are composd 
of one family only (the Daphnidz), the Branchiura for the pre- 
sent comprise only one family (the Argulidz). 
We think that the Branchiopoda (if we reserve the fossil 
Trilobites, which undoubtedly belong to them, and with whose 
oral organs and feet we are not sufficiently acquainted) may be 
characterized as follows :— 
BRANCHIOPODA. 
Oris partes palpis fere semper carentes, appendicibus branchialibus 
nullis; maxillarum par 1-0, maxillipedum 2-0. COculi duo magni 
laterales, seepe in unum coaliti, e multis bacillis crystallinis compo- 
siti, cornea supra eequali preediti. Segmentorum et pedum numerus 
valde varians: pedes fissi vel foliacei, appendicibus branchialibus 
plerumque instructi, nulla lamina intermedia bini conjuncti. Corpus 
testa membranacea, plerumque bivalvi, szepissime inclusum. Sexus 
distincti. 
I. PHYLLOPODA. 
Oculi compositi plus minus sejuncti. Pedum paria 10-60. Meta- 
morphosis completa. Libere natantia. 
1. BRancuipopips. 2.Aropipa. 3. Limnapipa. 4, NE- 
BALIDZ. 
