PACKARD.] PHYLLOPODS OF NOETH AMERICA. 319 



pair of feet. Lengtli of body. SS'"™ ; length of carapace (measured along 

 median line), IS^^j breadth, 17™™; length of caudal appendages, 14™™; 

 autennfe^ 10™™. 



Po Canon, Vermillion Eiver, Colorado; collected by Dr. C. A. White, 

 of Major Powell's Survey. Described from si)ecimens kindly loaned by 

 Prof. H. A. Ward, of Eochester, N. Y. 



This exceedingly interesting species differs from any other known to 

 me in the large, broad, bilobed telson, that of L. glacialis being small, 

 subtriangnlar, while in L. productus and L. couesii it is long and spatu- 

 late. It differs from the two latter species in the longer, broader, 1st 

 pair of feet, the longer body, and shorter carapace. 



The differences in the appendages in L. bilobatus and couesii are 

 very slight; in the 2d pair of feet the accessory gill of L. bilobaUis is 

 longer, less rectangularly triangular than in L. couesii, while the pear- 

 shaped gill is of nearly the same shape in both species. In both species 

 the four endites are long and slender, those of L. bilobattis being rather 

 wider than in L. couesii. The scale (6th endite) is blunt, knife-shaped, 

 and finelj'" denticulate on the outside in L. bilobatus, while in L. couesii 

 it is acute, shorter, and triangular. In the 2d pair of feet the scale in 

 L. bilobatus is very large, stout, knife shaped, and finely denticulated 

 on the inner edge, with fine setse externally; that of L. couesii is one- 

 third smaller and acutely triangular; the four endites are mucb broader 

 in L. bilobatus than in L. couesii. The accessory gill is larger and much, 

 tbe broader in L. bilobatus, the posterior end being very much produced 

 mL. couesii. In the 10th pair of limbs the endites are longer and narrower 

 in L. bilobatus than in couesii, and the scale is narrower. 



The following exotic species may be referred to here: 



Lepidurus viridis Baird, Proc. Zool. Soc, London, 1850. Van Diemen's Land. 



Lepidimis anqusii Baird, Proc. Zool. Soc, London, 122, 1866. Rain pools on the Gaw- 

 ler Plains, north of Adelaide, South Australia. 



Apus Schaeffer. 



Plates XV, figs. 1, la, lb; XVI, figs. 2-5a; XVIII, XXXII, XXXV. 



Apus Schaeffer, Der krehsartige Kiefenfuss, 17.%. Bosc, Hist, des Crust, ii, 244, PI. 

 XVI, fig. 7. Latreille, Hist, des Crust. Ins. iv, 195. Milne-Edwards, Hist. 

 Nat. Crust, iii, 356, 1840. 



As in Lepidurus, but the carapace is shorter, the abdomen being 

 longer and extending much, farther beyond the hinder edge of the cara- 

 pace; the 2d-5th endites of the 1st pair of legs are muck longer than in 

 Lepidurus, the 5th when stretched back sometimes reaching near the 

 telson ; tke latter is short, cylindrical, without any paddle-like exten- 

 sion. « 



Synopsis of the species. 



Carapace longer than in the other species; telson short, with 4 large 

 central spines above A. cequalis. 



Carapace shorter tban in cequalis, but the telson longer. . .A. newberryi. 



Carapace shorter than in foregoing species ; telson with only 3 central 

 spines A. lucasanus. 



Carapace much as in A. lucasanus ^ telson very short, with 5 central 

 spines A. tongicaudatus. 



