NO. 1302. 



AMERICAN PARASITIC ARG ULID.E- WILSON. 709 



ARGULUS CATOSTOMI Dana and Herrick. 

 Plate XIII. 



Argulus catostomi Dana and Herrick, Description of the Argulus catoBtomi, 

 Amer Jour. Sci., XXXI, 1837.— Milne-Edwards, Hist. Nat. des Crustaces, 

 III, 1840.-THORELL, Om tvenna Europeiske Argulider, etc., (Efvers. af 

 Koiigl. Vetensk.-Akad. Forhandlingar, 21st series, Stockholm, 1864. 



Carapace orbicular, wider than long; posterior sinus nearly one- 

 third the length of the carapace, broad with parallel sides. Abdomen 

 orbicular, wider than long, but relatively very small, not more than 

 one-fourth the length of the carapace; anal sinus narrow, almost slit- 

 like scarcelv one-third the whole length of the abdomen; papdhe basal. 



Disks of the anterior maxillipeds large, nearly one-fourth the width 

 of the carapace broad as the latter is; posterior maxillipeds also large, 

 every joint with a roughened area on its ventral surface; basal plate 

 broad triangular, with wide lobes on its posterior edge instead of 

 teeth sometimes two and sometimes three. Antennas small and weak, 

 the anterior pair without a hook on their front margin, while the 

 spines on the bases of both pairs are reduced to two insignificant 



pimples. 



The anterior swimming legs scarcely reach the edge of the carapace; 

 lol)es on the posterior pair large, boot-shaped. 



A large papilla present on either side of the opening of the oviduct. 

 The arrangement of the chitin rings in this species is characteristic; 

 the larger one extends along the edge oi the carapace lobe as far for- 

 ward as the sucking disks; at about the center of its inner surface is a 

 deep indentation into which the smaller ring fits snugly, the latter 

 being situated in the clear space just behind the posterior maxillipeds. 

 Flao-ella present. Eyes quite small. 



Length, 12 mm; length of carapace, 9.6 mm; l^readth of carapace, 

 11 2 min;' length of abdomen, 2.3 mm; breadth, 2.4 mm. 



Color a light sea-green, inclined to yellowish, growing quite dark 



in alcohol. ^ .-, ^ i -.u 4-\ 



This was the first American species to be descrilied, and with the 

 possible exception otfunduU and pugettensis it is the only one that 

 has ever been given anything like a decent figure. For this reason it 

 has been willingly accepted liy the European zoologists, and has taken 

 the same place in American parasitic copepods that A. fohaceus occu- 

 pies in the European fauna. 



It was first discovered on a sucker (probably Caiostomu.^ lostonenms 

 Le Sueur) in brackish water near New Haven, Connecticut. 



It has recentlv been found abundantly by the author upon the same 

 sucker in fresh water at Warren and Chicopee, Massachusetts. ^ 



But it is e-«n more abundant upon tue chub sucker {Enmyzon 

 sucetta oblo^igi)}^ Mitchill), which is nearly always found with the other 



