NO. 2194. NORTH AMERICAN PARASITIC COPEPODS— WILSON. 61 



The first antennae are short, slender, cylindrical, and three- jointed, 

 sparingl}'^ armed with setae, one at the tip of the distal joint and one 

 on the side of the second joint. The second antennae project from 

 the anterior margin of the head on either side of a short and pointed 

 rostrum. They are long, stout, and two-jointed, the joints about the 

 same length, the distal one ending in a stout chela, the claw shut- 

 ting down past a spiny projection on the inner side of the distal 

 joint. 



Proboscis a bluntly rounded cone, soft and fleshy in texture, as 

 large at the base as the whole ventral surface of the head, and con- 

 stricted at about the center of its length. It is well supplied with 

 striated muscles, by means of which it can be protruded and with- 

 drawn, or moved from side to side. At the tip there is a large lobe 

 on either side and a central oval plate on the ventral surface. This 

 plate is convex ventrally and covered at the center with minute 

 three-cornered spines. Above this plate and between the lateral 

 lobes the slender cylindrical mouth-tube projects a short distance. 

 This is a very thin-walled, transparent tube, wrinkled transversely, 

 and held open by circular chitin ribs. It flares somewhat at the 

 tip, where it is surrounded by a delicately scalloped membrane. It 

 is extensile and can also be moved from side to side independently 

 of the rest of the proboscis. 



On either side of the base of the ventral plate is a maxilla, which 

 is three-jointed, the terminal joint narrower and longer than the 

 ether two, which are about equal. At the outer distal corner of 

 the basal joint is a short spine; the terminal joint ends in a short, 

 Etont, and blunt claw. 



The swimming legs each consist of flattened oval basal plate and 

 very short and blunt rami, destitute of setae; the first two pairs are 

 biramose, the last two pairs uniramose. 



Color. — The head and proboscis are a deep fish-blood red when 

 freshly taken from the host, the neck a light horn color slightly 

 greenish, the central digestive canal more or less red when filled with 

 blood ; trunk dark red internally, surrounded by the yellowish-white 

 ovaries and oviducts ; egg strings a light greenish yellow. 



Entire length, without egg strings, 40 mm. Length of trunk, 20 

 mm. Diameter of trunk, 1.50 mm. Greatest spread of horns, G mm. 

 Length of egg strings, 28 mm. 



(radiatus, radiate, alluding to the usual arrangement of the 

 horns. ) 



/Remarks. — The beautiful figures illustrating this species were 

 drawn some time ago by Kichard Kathbun, now assistant secretary in 

 charge of the Smithsonian Institution, and were generously turned 

 over to the present author together with valuable notes and de- 



