CYPRIM1. 
145 
three or four terminating ones of which arise several 
pretty long filaments, which vary in number in the dif- 
ferent species. Whenever the animal moves, it invariably 
puts these organs into rapid motion, dilating and bringing 
together again the long filaments, and waving theim to 
and fro with great rapidity. They are thus considered 
by Muller and Straus to act as true fins, and to be the 
principal organs of progressive motion. Jurine, however, 
says that, from their position in the anterior part of the 
body, and from their motions being thus confined by the 
opening of the shell, they cannot be considered as acting 
the part of true fins, and that their use in progressive 
motion is by no means equal to that of the inferior an- 
tennae, called by him the anterior feet. In the larger 
species we see these filaments to be beautifully plumose, 
a circumstance which has never been pointed out by any 
of the various authors who have written upon the genus, 
and which strengthens Latreille’s suggestion that they 
may act as respiratory organs, as well as the branchial 
plates of the jaws. The inferior, or second pair of antennae 
(t. XVIII, f. 1 c), arise immediately beneath the others ; 
they are very strong, and resemble in appearance feet as 
much as antennae : indeed, they have almost invariably 
been considered and described as the first pair of feet. 
Their position, however, in front of the mouth and organs 
of mastication, as in the other genera of Entomostraca, 
and their resemblance to the inferior antennae of the 
(Jydopidae, warrant us, along with M. Edwards, in con- 
sidering them as antennae. They consist each of five 
articulations:* two belonging to the basilar portion, short, 
and directed downwards; a third, longer, directed for- 
wards ; and two terminating joints, the first of which, in 
most of the species, gives off at its lower extremity a 
bundle of setae, which are frequently plumose ; and the 
last being terminated by several tolerably strong hooked 
spines or claws. This pair of antennae, therefore, by 
* Jurine says eight. 
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