4 PROCEEDINGS OF THE NATIONAL MUSEUM vol.72 



The telson of H. danicus is thin and pellucid, and Hay had obviously 

 regarded the internal edge of the basal parts of the uropoda as an 

 acute-angled incision into the telson : " Terminal segment of abdomen 

 notched behind." Though I have had no opporutnity to examine 

 Hay's types, I admit without hesitation Verhoeff 's construction.^ 



Richardson includes H. puteus Hay in her monograph on the 

 Isopods of North America, but gives only a reprint of Hay's de- 

 scription and reproductions. She declares: "Although the types 

 (two or three fragments) are in the United States National Museum, 

 they have been so mutilated through dissection that I have found 

 it more satisfactory to quote the above." 



The figures that Hay has appended to his original description are 

 numerous and fairly good and make certain the identity of H. puteus 

 and H. danicus. They are, however, somewhat schematic and pre- 

 sent some minor errors. As H. dardcus has not been minutely de- 

 scribed and figured (the figures in Sars, 1899, being rather schematic) 

 I have given here short descriptions and sketches of the parts most 

 significant as far as classification is concerned. The descriptions and 

 figures are from the specimens from Plummer Island, Maryland, 

 with the exception of the mandibles, which are from Swedish speci- 

 mens, as the American micropreparations did not show the pro- 

 portions very well. 



Description. — Antennulae (fig. la) with the basal joint short and 

 broad, the second joint somewhat longer than the first but much nar- 

 rower, the terminal joint as long as the second but very much nar- 

 rower, carrying at the end five sensory filaments, one of which is 

 placed a little lower than the others. 



Antennae (fig. lb) with the basal joint short and very broad, 

 transverse, the second joint longer but rather broad, the third joint 

 somewhat shorter than the second, the fourth joint more than twice 

 as long as the third, concave at the outer side, the fifth joint some- 

 what longer than the fourth, narrow at the base and abruptly thick- 

 ening upwards. The second and third joints carry a few, the fourth 

 and fifth joints numerous, pointed tubercles formed of short lamellar 

 bristles, and arranged in longitudinal rows. Flagellum shorter than 

 the last joint of the peduncle, three-jointed, the last joint terminat- 

 ing in a dense bunch of long delicate hair-like bristles; all the joints 

 covered with short lamellar bristles, the second joint also carrying 

 a few olfactory setae {Leydigsche Borsten). 



Right mandible (fig. 1 c) with the outer cutting edge formed of 

 two large teeth, the inner cutting edge being represented by a 

 cylindrical, somewhat curved prominence, ending in a crown of 

 small teeth at the base of which is a single curved plumose seta. 



* Mr. C. R. Shoemaker, of the TJ. S. National Museum, has examined the cotypes 

 of Haplophthalmus puteus Hay and writes that there is no incision in the telson. 



