Description of the Argulus Catostomi. 301 



margins to become tubular ; and that the enclosed spicula represents 

 the mandibles. The part which we have called the lower lip, is 

 analogous to the languette ; and the maxillae with the long bones 

 thereto attached are not unlike these organs as usually observed. 



In the Argulus foliaceus the entire oval mass, which we have above 

 described, is assumed by Jukine to be the heart ; which we are com- 

 pelled to consider a total error. The palpitation, or alternate con- 

 traction and dilatation, which he speaks of, appears to us nothing 

 more than the motion of the maxillae, which just before death often 

 becomes incessant, and in the instance mentioned by him was prob- 

 ably caused by the " alcoholic asphyxiation." 



The anterior legs are short, hollow, flexible cylinders, containing 

 four tumid membranes attached near the center of these legs at the 

 bottom and extending up along the sides. By means of these the 

 animal is enabled to exhaust tlie cavities and thus attach itself to its 

 prey. The extremity terminates in a broad, circular, horizontal 

 rim., with a margin nearly entire, provided with about eighty bony 

 rays, each composed of eleven joints, (Fig. 6.) When the animal 

 is nearly dead, this rim assumes a vertical position, and from the 

 relaxing of the membrane appears to have a crenated margin.* 

 These legs in their natural position are at right angles with the body 

 and consequently the lower portions are concealed by the termina- 

 ting border. On fig. 1, may be seen lines proceeding from between 

 the base of the anterior antennae which probably mark the limits of 

 a muscle connected with these legs. 



The prehensile legs arise below and on each side of the mouth, 

 and are six-jointed. The thigh or second joint, is short, massive 

 and irregular, and its posterior margin is occupied by three broad 

 and flat teeth, with interstices about equal to half the average width. 

 These teeth are irregularly quadrilateral with rounded angles. In 

 this respect this species differs from the A. foliaceus, in which 

 there are four narrow, acute, and incurved teeth about the base of 

 this joint. 



On the lower surface is a triangular, subconvex elevation, covered 

 with papillae. The third joint gradually tapers towards its apex, 

 where it is papillose ; the fourth joint is shorter than the third, and 



* Jurine's figure of this rim or disk errs in exhibiting it in the vertical position 

 as that which appears during life : this is never observed except when the powers 

 .^f life are nearly exhausted. 



