150 M.T.Thorell on the Morphology of the Argulide. 
Under these circumstances it will not be uninteresting to 
learn that our quarter of the globe possesses two additional 
species of the family Argulide,—one a marine form, from South- 
ern Europe (the Mediterranean), the other a freshwater form, 
like A. foliaceus, and belonging to the middle and northern parts 
of Sweden. The first of these two species, Argulus purpureus, 
has certainly been already described by Risso under the name of 
Binoculus bicornutus and Agenor purpureus ; but it seems to have 
been altogether overlooked by later observers, the reason for which 
should no doubt be sought partly in the limited circulation 
which many of Risso’s works have attained, partly im that 
author’s usually very insufficient descriptions, which often render 
the recognition of the species intended very difficult: Agenor 
purpureus is referred to the family Bopyride! A new descrip- 
tion of this species, of which I found an example at Nice, on the 
pectoral fin of Pagellus erythrinus, will, therefore, not be consi- 
dered superfluous. 
The other, the Scandinavian species, which I call Aneta 
coregoni, is, on the contrary, new to science. My attention was 
drawn to it through a memoir by Dr. C. L. Nystrém*, wherein 
mention was made of an unusually large Argulus as one of the 
parasites which infest the Coregonus in Jemtland. Specimens 
of this Argulus were brought by Dr. Nystrom to the Royal 
Zoological Museum in Stockholm, where also specimens exist 
from Dalsland collected by Mag. H. Widegren ; and through 
the united kindness of Prof, Lovén and Err. Nystré6m and 
Widegren, I have had opportunities of examining both Jemt- 
land and Dalsland specimens of this large and well- marked 
species. 
I: 
Before proceeding to the description of the animals in ques- 
tion, it will be advisable to state my own conceptions of the 
various divisions of the body and its accessory organs, which have 
been very differently interpreted by the authors who have hither- 
to handled this group. ‘The first great division of the body, 
which bears the antenne, the organs of the mouth, and the fol- 
lowing two minute pairs of limbs, and which in these animals is 
developed into a large shield produced behind into two lobes, I 
call the head or head-shield (scutum cephalicum) ; the other, to 
which the cloven swimming-feet are attached, the trunk (truncus), 
which is followed by a tail (cauda) transformed into a leaf-like 
respiratory plate, bearing two small appendages, which, in the 
newly-hatched larva, are situated at the tip of the tail (as is the 
* «Jakttagelser rorande Faunan i Jemtlands Vattendrag,” Akademisk 
Afhandling, &e. (1863), p. 19. 
