no. 2354. NEW SPECIES OF PARASITIC COPEPODS— WILSON. 5 



The abdomen is two-jointed; the joints about the same length and 

 half as wide as the genital segment. The basal joint has lobes at its 

 posterior corners similar to those on the genital segment but smaller. 

 The anal laminae are broad and oval, as long as the last abdomen 

 segment, and nearly half as wide; each is armed with four non- 

 plumose setae. 



The frontal plates are wide and project anteriorly, with a shallow 

 median sinus. The first antennae are of the usual pattern, but the 

 second pair are stronger and have a large terminal claw. The first 

 maxillae are close to the base of the mouth tube; each consists of a 

 single spine, long, slender, and strongly curved. The second maxil- 

 lae are also long and slender, with a single terminal claw. The 

 maxillipeds are stout and their terminal claw is abruptly curved 

 near its tip. 



The furca is narrow and slender, the base a little longer than the 

 branches, which are cylindrical, straight, and not very divergent. 



All four pairs of legs are biramose. The endopods of the first 

 pair are very short and two- jointed, the exopods much longer and 

 stouter; the basal joint carries a spine at the center of the anterior 

 margin and another similarly located on the posterior margin. The 

 second and third legs are similar to those of other Caligids. The 

 endopod of the fourth legs is much shorter than the exopod and has 

 but two joints, while the exopod has three. The basal joint is some- 

 what triangular, with a slight projection at the inner posterior 

 corner. 



Remarks. — In 1853 Gerstaecker published 3 the description and 

 figures of a new genus and species of parasitic copepods, to which 

 he gave the name Elytrophora hrachyptera. In his diagnosis of 

 the genus he wrote (p. 58) : 



Corporis pars thoracica cephalothorace tribusque annulis thoracicis satis dis- 

 tinctis composita, abdomen annulis duobus, appendicibusque duabus termi- 

 nalibus, setiferis. Dorsum appendicibus foliaceis in mare duabus, quattuor in 

 femina ornatum. . . . Pedum branclnalium paria quattuor, quorum tria 

 annulo thoracico primo, altero quartum affixum. 



It is difficult to understand how the thoracic segments could be 

 " satis distinctis " if three pairs of swimming legs were attached to 

 the first segment. 



In 1863 Kr0yer described and figured 4 a new parasitic copepod 

 from the Vienna Museum under the name Arneus thynni Kollar, 

 saj'ing that Kollar had given it a museum label as Dinematura 

 thynni. Kr0yer gave no diagnosis of the genus, but the description 

 and figures leave no doubt that his parasite was the same as the 

 one previously described by Gerstaecker. In addition the name 



3 Troschel'a Archiv ftir Naturgeschichte, vol. 19, pt. 1, p. 58, pi. 3. 



4 Naturhistorlsk Tidsskrift, vol. 3, pt. 2, p. 157, pi. 8, fig. 5. 



