730 PROCEEDINGS OF THE NATIONAL MUSEUM. 



Genus DOLOPS Audouin. 



This genus was first described by Audouin in 1837 and afterwards 

 more in detail b}- Helier in 1857. It differs from both the other 

 genera in the fact that the anterior maxillipeds are not modified into 

 sucking disks, but terminate in strong, sickle-shaped hooks (fig. 73). 

 It resembles Argulus and is unlike Chonopeltis in the presence of both 

 pairs of antenna^ and of spines on the ventral surface. On the other 

 hand it is like Chonopeltis in the complete suppression of the preoral 

 sting. The carapace is large, orbicular, or inversel}" egg-shaped, and 

 in the species so far known it almost covers the legs. In two of the 

 species, longlcauda and dorad/.s, the abdomen is very long and narrow 

 and is cut clear to the base. In hollari it is orbicular and resembles 

 closely that of Argultos megaloj^s and A. laticauda^ while in geayi it is 

 more 1 ike that of A. alosx. 



The first antennas lack the hook on the anterior margin which is pres- 

 ent in most of the Arguli, and the spines on the basal joints of both 

 pairs are nmch reduced in numl^er (fig. 71:). 



The anterior maxillipeds, while not modified into sucking disks, are 

 yet very unlike the posterior ones. They are short and stout; the 

 basal joints are very wide and thick set, but the subsequent ones dimin- 

 ish rapidly in size, so that the terminal joint is only wide enough to 

 receive the base of the large sickle-shaped hook. Opposed to the hook 

 at its base is a short, cylindrical peg, the two fitting together much like the 

 chela of a lobster or ci-ab (fig. 73). The hooks on the two maxillii)eds 

 curve in toward each other, and when once driven into the fiosh of the 

 host by the powerful muscles withui the basal joints they must afi'ord a 

 very secure hold. But it will evidently be quite a task to withdraw 

 them, and one that will consume some time. Hence they are not at all 

 suited for that scuttling motion so characteristic of Argulus, and Dolops 

 must be a genus which can not move about f reel}^ over its host's body. 



Again, the wound itself and the subsequent irritation caused by the 

 insertion of these powerful hooks is amply sufiicient to cause a strong 

 flow of blood, and obviates the necessity of any sting. Consequently 

 we find the mouth parts consisting of a short conical proljoscis between 

 the bases of these anterior maxillipeds, somewhat in front of its posi- 

 tion in Argulus, and there is no trace of any preoral sting. 



The proboscis is formed from the upper and under lips strengthened 

 by a frame work of chitin rods similar to that already described, Imt 

 there are no maxillte. 



The posterior maxillipeds have the basal plate armed with three 

 teeth, but have no claw on the terminal joint (fig. 72). In its place the 

 tip of the terminal joint is divided into twopapilhe of unequal length. 

 The inner, larger one is covered on its ventral surface with two rows 

 of curved spines, four to seven in each row, while the shorter, 

 outer papilla ends in a single row of four or more larger, sickle- 



