﻿38 PROCEEDINGS OF THE NATIONAL IvIUSEUM vol. 102 



European part of the U. S. S. R.; Jakutsk (Sars, 1897), several places 

 in the territory of Akmolinsk (Sars, 1901, 1903), territory of Koksche- 

 tavsk (Sars, 1903), and Kasalinsk in Turkestan (Decksbach, 1924). 



Tiemarks. — Outside America, there is a species with a similar telson 

 and supra-anal plate, L. macrurus Lilljeborg. The general resem- 

 blance between this species and L. couesii was noted by Lilljeborg, 

 who mentioned (1877, p. 14) one difference only, that the former has 

 6 to 8 rings exposed behind the carapace and the latter only 5. This 

 character "is generally recognized to be somewhat unreliable" (Gur- 

 ney, 1923, p. 502) because of the varying state of contraction of the 

 specimens (p. 5), and I have seen American specimens of L. couesii 

 with 7 exposed rings as well as specimens of L. macrurus, identified by 

 Lilljeborg, with five exposed rings, 



I have examined 25 Asiatic specimens identified as L. macrurus by 

 Lilljeborg. They, as well as some specimens from a more southern 

 locality, agree perfectly well with the American specimens of L. couesii 

 as described, and ought to bear the same name, which is 2 years older 

 than that given by Lilljeborg. 



The relationship of this species to the European L. apus, to which 

 it bears a certain resemblance, is in need of clarification, but I have 

 not had enough material of the latter species to make a detailed 

 comparison. 



LEPIDURUS BILOBATUS Packard 



Figure 13; Plate 2 (Figures 3, 4) 

 Lepidurus bilohalus Packard, 1883, p. 318. 



Description. — A supplementary description of a female labeled 

 "Type, Utah, coll. Henshaw" (U.S.N.M. No. 11606) is given here. 

 Body-rings 11 + 16.5+4.5 = 32. Legless rings with many (19) densely 

 crowded spines on the ventral side, dorsally 7 spines. Supra-anal 

 plate slightly bilobed, with 8 dorsal spines, 4 of which are smaller than 

 the others, all of them placed on a slightly marked keel. Nuchal 

 organ oval, placed between hind parts of eye-tubercles. About 62 

 pairs of legs. In other respects there is reasonable agi*eement with 

 Packard's description. Further particulars are given in table 1 (p. 36). 



Remarks. — The real status of this type seems to be a little uncertain, 

 because Packard's t^^pe locality was not Utah, but Po Canon, Ver- 

 million River, Colo. However, the specimen most probably comes 

 from Packard's collection, and I feel reasonably certain that it belongs 

 to this species. The large number of abdominal rings agrees well 

 with Packard's statements that "the abdomen is longer than usual" 

 and "there are about sLxteen segments beyond the posterior edge of 

 the carapace." Another species with many abdominal rings is de- 

 scribed later on in this paper (p. 39), but L. bilobatus is easily dis- 

 tinguished by the position of the nuchal organ, the typical arrange- 

 ment of the spines on the posterior emargination of the carapace, and 



