﻿NORTH AMERICAN NOTOSTRACA — ^LINDER 33 



L. lemmoni Holmes (p. 50) is regarded as insufficiently known to be 

 included in the key. 



LEPIDURUS ARCTICUS (Pallaa) 



Plate 1 (Figure 1) 



Monoculus ardicus Pallas, 1793, pp. 39, 679. 



Lepidurus glacialis Packard, 1883, p. 316. — Sars, 1896, p. 68, pis, 11-13. — • 



Chamberlin and Duncan, 1924, p. 101. 

 Lepidums ardicus Johansen, 1922, p. 4. — Linder, 1932, p. 192. 



Description. — For a detailed description readers are referred to 

 Sars (1896). So far as I can see, there are no essential differences in 

 structure between American and Em-opean or Asiatic specimens. 

 Simon (1886, p. 429) says, "Lamina analis parva attenuata brevior 

 quam telson (in speciminibus sibiricus) vel parum longior (in sp. 

 americanis)," but he probably had too little material to cover the 

 individual variations; in the extensive material I have seen I cannot 

 find such a difference. S0mme (1934) noticed varying sizes of the 

 spines on the dorsal side of the legless body-rings in specimens from 

 various European localities, but it is uncertain whether these dissimi- 

 larities lie within the range of individual variation or characterize 

 geographical races. In any case, I do not think they can be given 

 specific value. 



The number of body-rings is 11 + (10-12)+ (4-5)=26-28, and the 

 number of legs is 41-46. Length of supra-anal plate is 7-13 percent 

 of length of carapace. 



Localities. — The localities in the collection of the U. S. National 

 Museum are recorded by Johansen (1922). 



Distribution. — For distribution, see Linder (1932). 



LEPIDURUS PACKARDI Simon 



Figures 10, 19, a; Plates 2 (Figures 1, 2) and 7 (Figure 6) 

 Lepidurus packardi Simon, 1886, p. 448. 



Description. — The principal points of the description are as follows: 

 Carapace broadly oval, carina conspicuous in posterior third but dis- 

 appearing anteriorly, posterior emargination with minute, numerous 

 spines interspersed with slightly larger ones at regular intervals 

 (8-9 on each side). Nuchal organ small, broadly oval. Abdomen 

 short, hardly projecting behind carapace. Abdominal legless body- 

 rings with 8 strong, sharp spines dorsally and 20-25 smaller ones 

 ventrally. Supra-anal plate small, with parallel sides and rounded 

 apex, and with 8 spines in the dorsal middle line. Endites 2, 3, and 4 

 of first leg rather thick and flattened and projecting beyond the margin 

 of the carapace, endite 5 projecting beyond first third of carapace. 

 Length of carapace 15.5 mm., width 14 mm. 



Type locality. — California. 



Type. — Type in Museum d'Histoire Natm'clle, Paris. Thanks to the 

 courtesy of Dr. ]Marc Andre, of the Museum d'Histoire Naturelle, I 



956651—52 3 



