NO. 1368. 



DESCRIPTIONS OF ARGULID.E—WILSOX. 



631 



marofin and a smaller and sharper one on the posterior marg-in of its 

 basal joint. Thv latter is reenforeed by si-veral s(»tie. All these hooks 

 and spines are of a rich yellow eolor. 



J'Jyei'i. — These are small, made u]) of 

 numerous facets, and quite widely sepa- 

 rated. 



Fig. 3. — .Vntenx.k of ke.malk ARorn'S 



AMERIC.\XrS. 



Fig. 4 — Mouth parts of argulus americanus. I. 

 LOWER lip; /;;, LABIAL PALP; md, mandibles; 

 iiu, maxill.e; r, chitix ribs. 



Mouth (tio-. 4). — This organ 

 has a peculiar, almost trape- 

 zoidal, form, and its lateral 

 margins are strongly serrated. 

 The lower lip (/) has a sharper 

 curve than in A. foliaceus and 

 the labial palps (7/y) are rela- 

 tiveh' smaller. But the great- 

 est difference is in the mandi- 

 bles {md): instead of being 

 broadh' sickle-shaped, with 

 teeth along the inner margin 

 only, the^' are widened into a spatula form, with long and sliarp teeth 

 on both the inner and outer margins and around the end, twelve or 

 fifteen of them in all. The maxilla {in;i) are also much stouter than 

 in foliaceus, but the single tooth at the tip is shorter and ])lunter. As 

 a whole the proboscis is only 

 slightly club-shaped and is 

 rather smaller than would be 

 expected on so large an Argu- 

 lus. The chitin framework, 

 while agreeing in its general 

 make-up with that oifoliactus^ 

 differs in several details. The 

 longitudinal ril)s (/') are not 

 forked at their distal ends, and 

 the transverse ribs are less 

 complicated. 



^4;^ ta'ior iuaxilliped^. — These 

 are small, not more than one-sixth the width of the carapace, and close 

 together. The shape of the chitinous rods which support the mem- 

 branous edge and the arrangement of the fringe are peculiar. Tliere 



-B<)i;nK,K OK SICKING DISK in ARoru-s 



AMERICAN IS. 



