Description of the Argulus Catostomt. 305 
one of them deposited on the sides of the vessel in which she was 
contained, about one thousand five hundred, and a considerable mass 
of eggs still remained within. ‘The eggs have an oval form, are 
white when first laid, but soon become of a dirty yellow, and finally 
assume longitudinal crenated ribs. ‘They are attached to each other 
and to the object on which they are placed, by a glutinous substance, 
and are disposed end to end, in single rows of about four or five, 
sometimes however of ten or fifteen. ‘These rows have a somewhat 
promiscuous arrangement. 
Thirty five days after deposition, the young animal anpeusih 
through a longitudinal fissure in the shell, the eyes and some o 
the darker parts having been visible about ten days previous. Its 
length is ,'. of an inch, and the general shape of the shell an 
oval, somewhat broader anteriorly. Beyond the shell, extend the 
three terminal joints of the abdomen, ending in a broad tail, with two 
terminal elongated protuberances, from each of which proceed three 
unequal sete. 
The eyes are of a reddish brown color, and proportionally much 
larger than in the adult animal. The anterior pair of antenne have 
a general resemblance to the corresponding pair in the perfect ani- 
mal, except that here the posterior branch is proportionally much 
larger and constitutes the chief part of the organ. 
Behind these arise two pairs of oars; the anterior pair have a 
basal joint in common with the posterior antenne which extend down- 
ward and outward from the oar. Jurine seems to have erred in 
Supposing this pair independent of the oar. ‘The oars are slender 
and cylindrical, extending beyond the shell. From each proceeds a 
pencil of plumose hairs; the number of these, in the anterior pair 
is four, in the posterior, three. These hairs may be made to approxi- 
mate or diverge at pleasure. The posterior pair may possibly rep- 
resent the maxille which are wanting ; they appear to arise from the 
origin of the long bones which in the perfect animal are found con- 
nected with the maxille. 
The sucker extends beyond the anterior margin of the shell id 
is distinct, but the organs contained in the oval mass below are ex- 
tremely obscure. | 
The suction legs are replaced, as is the case with the A. foliaceus, 
by a pair of prehensile legs, which end each in a spine provided 
with a sheath in which it commonly lies, (fig. 11.) The nex | pair 
are somewhat like the prehensile in the pert animal, which legs 
Vou. XXXI.—No. 2. 9 : 
