718 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxv. 



color that thoy can hardly 1)0 distinguished from frosh specimen.s, save 

 for their greater opacity. 



This species was first found b}" the author upon some common pick- 

 erel {Lucvus reticidatus Le Sueur) caug-ht throuoh the ice at Powder- 

 mill Pond, Warren, Massachusetts. They have since ])een found on 

 the same fish in Wickaboag and Podunk ponds, Brooktield; in Lake 

 Lashawa3% between Brookfield and Spencer; in Ashle}'^ Ponds, Hob 

 yoke; and in Congamon Ponds, Southwick, all in Massachusetts. 



In fact, they have not l)een looked for in a single pond where thej' 

 have not been found, and in all probability they infest this fish more or 

 less throughout its habitat. 



The}" can be distinguished from all other species at a glance by their 

 brilliant coloration. 



Length, 6 mm.; length of carapace, ^A mm.; breadth of carapace, 

 4.9 mm.; length of abdomen, 1.(5 mm.; width, l.ti mm. 



ARGULUS AMERICANUS, new species. 

 Plate XXI; Plate XXVI, figs. 84-86. 



Carapace obovate, as wide as long; posterior sinus narrow, extend- 

 ing one-third the length of the carapace, quite square at the base, but 

 the sides converge quickly and the carapace lobes overlap considerably 

 at their tips. Abdomen l)roadly triangular, one-half wider than long; 

 anal sinus broadly triangular; papillse subterminal. Sucking disks 

 small, one-sixth the width of the carapace; posterior maxillipeds also 

 rather small, but well armed; basal plate narrow, triangular, with wide 

 squarely truncated plates on its posterior border in place of teeth, thus 

 resembling verslcolo7' and catostomi. 



AntenniB rather small but furnished with strong hooks and spines; 

 two spines instead of one at the bases of the posterior pair. Swim- 

 ming legs long and very slender; lobes on the posterior pair ver}" 

 large, boot-shaped, with a distinct heel. 



In the male, beside the regular copulatory organs, there are very long 

 projections on the basal joints of the second and third legs at the distal 

 ends. Those on the second legs are conical and on the posterior sur- 

 face, those on the third legs are flattened, club-shaped, and on the ante- 

 rior surface. 



There are also smaller projections on these same joints opposite the 

 large ones, and a rounded knob on the anterior surface of the second 

 joint of the third legs. The abdomen in the male is scarcely elongated 

 at all. 



Flagella present; papilla? at the oviduct opening long and stout. 

 Chitin rings in the carapace lobes similar to those in the last tw^o spe- 

 cies, but not extending quite as far forward. To compensate for the 

 mediocre size of the two pairs of maxillipeds, we find the ventral sur- 



