PACKAND.] PHYLLOPODS OF NORTH AMEEICA. 325 



Total length of carapace, IQ""^"^; width of the same, 17"°°^. 



Length of keel on the carapace, 8^'^^', from anterior end of keel to 

 front edge of carapace, 6'"'". 



Length of abdomen beyond the carapace, 21|"'™. 



Length of caudal appendages, 20""". 



Diameter of the ovisacs, 2|"™. 



Our female differs from the males in the carapace being longer, with 

 28 segments, uncovered, beyond the carai)ace; and 10 segments beyond 

 that bearing the last pair of appendages, while the under side of the 

 telson is much smoother than in the males, but the upper side as in the 

 males; the caudal appendages less spiny than in the males. 



The ovisacs contained a few eggs, which were of the same size as in 

 A. lucasanus and otherwise the same, except that the germ had com- 

 menced to develop ; they were arranged in the cavity of the ovisac side 

 by side in two rows, the lower or inner row the larger. 



I have had the opportunity of examining Professor Dana's original 

 type of Leconte's, contained in the museum of Yale College. It was, 

 when received, broken and dried up, but with the carapace preserved, 

 while the caudal appendages were wanting. The specimen was labeled 

 "Rocky Mountains, near Long's Peak." This would j)lace it within the 

 present limits of Colorado. 



Four specimens from the museum of the Chicago Academy of Sciences, 

 received through the late Dr. William Simpson, were labeled "Texas, J. 

 H. Clark 'No. 3." They only differ from Dana's type specimen in the 

 dorsal carina of the carapace being considerably shorter than in the 

 type, being twice as long as the distaiice from the front margin of the 

 carapace to the anterior end of the keel. 



In the other specimen this distance is one-third or one-fourth as great 

 as the length of the keel. The specimens vary somewhat in the relative 

 length of the keel, in the length of the abdomen, and the size and num- 

 ber of spines on the under surface of the telson, while the endites of 

 the 1st pair of feet vary slightly in length. The size and form of the 

 telson, and the number and arrangement of the sijines afford good spe- 

 cific characters in this genus. 



Three specimens labeled " Pools near Yellowstone Eiver, Dr. Hayden, 

 6," were also received through Dr. Stimpson, of the Chicago Academy. 

 The range of the species would seem to be from the Yellowstone Eiver 

 along the eastern flank of the Rocky Mountains to Texas, probably the 

 upper part of the State. 



James, in Long's "Expedition to the Rocky Mountains," says of this 

 species: "Rain-water puddles on the Platte River, near the Rocky 

 M ountains. ... In rain-water puddles we remarked a new species 

 of Branchipoda belonging to the genns A^us; small crustaceous ani- 

 mals, which exhibit a miniature resemblance to the King or Horse-shoe 

 Crab {Limulus polyphemus) of our own sea coast, but which are furnished 

 with about 60 pairs of feet, and swim ujDon their back. The basins of 

 water which contained them had been very much diminished by evap- 

 oration and infiltration, and were now crowded to excess, principally 

 with the Apus, great numbers of which were dying upon the surround- 

 ing mud, whence the water had receded. This species is distinguished 

 from the productus of Bosc and montagui of Leach, by not having the 

 dorsal carina prolonged in a point behind ; and from cancriformis by the 

 greater proijortional width of the thorax, and more obtuse emargina- 

 tiou behind. The length of the thorax along the middle is three-tenths 

 of an inch, and its greatest breadth somewhat more. It may be named 

 Apus obtusus." — Note 7, p. 336. 



