NO. 1573. PARASITIC COPEPODS— WILSON. 427 



angle at the center of the carapace, about one-third the distance from 

 the anterior margin. Second and third thorax segments fused to- 

 gether and canying a single rectangular lol)e or plate on either side, 

 which extends obliquely backward nearly to the tips of the posterior 

 lobes of the carapace. Fourth segment free, considerably narrower 

 than the second and third segments and covered with a pair of fused 

 dorsal jilates. Each of these is nearly a perfect circle in outline, in 

 strong contrast to the angidar j)air on the second and third segments. 

 They do not extend out as far as the latter, but are about the same 

 width as the genital segment, over whose anterior margin they extend 

 for a little distance. Genital segment elliptical, or slightly ovate, 

 with an evenly I'ounded margin, the length to the breadth in the pro- 

 portion of 8 to 5. Abdomen invisible in dorsal view, but the two 

 large anal lamime project nearly their entire length behind the pos- 

 terior margin of the genital segment. Each of them is as wide as 

 long, and as large as the entire abdomen, and is armed with four slen- 

 der j)lumose seta^. Seen ventrally, the abdomen is small, triangular 

 in shape, and attached about its own length in front of the pos- 

 terior margin of the genital segment. The apex of the triangle is 

 represented by the narrt)w neck where the abdomen joins the genital 

 segment while the broad base is at the posterior margin where the 

 anal lamime are attached. 



The first antenna^ are short and stout, the basal joint nearly twice 

 the diameter of the terminal and thickly studded with seta\ the ter- 

 minal joint furnished with setw along its posterior marign as well as 

 at the tip; second antennjie large, with a long and stout terminal 

 claw. First adhesion pads elliptical, close to the margin of the cara- 

 j)ace, and more tnan twice the size of the second pair; the latter 

 nearly circular and removed some distance from the first ones. In 

 the young female these pads appear as short and slightly curved 

 claws, and are then like the corresponding fu"st maxillae in the Caliginae. 

 In the adults they are transformed into large pads, fastened for 

 their entire length to the ventral surface of the carapace. Similarly 

 the pads at the l)ases of the first maxillipeds are straight spines in the 

 young. 



The second maxilhe are close beside the base of the mouth-tube 

 and are apparently two-jointed; the basal joint is large and swollen, 

 twice as long as w4de; the terminal joint is a short curved claw. 



The mouth-tube is long and pointed; the framework consists of a 

 slender rib along either side extending from the base to the tip and 

 almost perfectly straight, with the ends somewhat enlarged; the ends 

 at the tip are joined by their inner margins, while those at the base 

 are joined by a chain of three circular plates, the central one being 

 considerably larger than the other tw^o. 



