Description of the Argulus Catostomi. 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 often or fifteen. These rows have a somewhat 

 promiscuous arrangement. 



Thirty five days after deposition, the young animal appeared, 

 through a longitudinal fissure in the shell, the eyes and some of 

 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 set?e. 



The eyes are of a reddish brown color, and proportionally much 

 larger than in the adult animal. The anterior pair of antennae 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 antennae 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 maxillae 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 maxillae. 



The sucker extends beyond the anterior margin of the shell and 

 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 next pair 

 are somewhat like the prehensile in the perfect animal, which legs 



Vol. XXXI.— No. 2. 39 



