﻿Q PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



Barnard (1929) also points out that we cannot give an accurate 

 count of the body-rings exposed behind the carapace. In order to 

 give some, even if not an accurate, idea of this conspicuous feature 

 I have mentioned the number in some specimens. But I give this 

 number, as well as the figm-es of the total length, only with a stated 

 reservation as to its accuracy. 



As S0mme (1934) has shown for Lepidurus arcticus, the carapace 

 is little affected by the preservation fluid and thus can give an idea 

 of the size of the animal. This is only natural, because it is contin- 

 uously and highly chitmized. Following the general custom, I 

 measure its length along the mid-dorsal line. Of course, we camiot 

 be sure that variations in this figure closely follow the variations of 

 the real total length of the body; the relation may vary according to 

 varying ages of the specimens, to say nothing of the varjdng contrac- 

 tion. To obtain the greatest width of the carapace, the usual method 

 seems to have been to measure it in a straight line. This is not 

 reasonably accurate, because the height of the carapace may var.y, 

 sometimes to a considerable degree. It is better to measure the 

 greatest width from the carina to both sides (fig. 2), In cases of 



Figure 2. — Cross section of the carapace of a notostracan, showing how the width of the 



carapace is measured. 



distortion, I have flattened the carapace to a shape similar to normal 

 appearance before taking the measurement. 



I count 5 endites on each leg (fig. 26). The coxal lobe is the first 

 endite ; it is essentially similar to the other endites in the arrangement 

 of the setae and has on its margm similar small elevations covered 

 with small needlelike structures. What Packard (1883) calls the 

 sixth endite is quite dissimilar to the more basal, real endites; it has 

 only a single row of setae and spines along its margin, and no trace 

 of the smiall elevations mentioned above; I call it the endopodite, 

 as many other authors do. Packard's "flabellum" is the exopodite, 

 and his "gill" is called epipodite in this paper. Further, we some- 

 times find what may be the vestige of a preepipodite (fig. 22) in the 

 form of a smafl elevation with a few setae (cf. Erilvsson, 1934, p. 236). 



Specimens from the follo\ving museums were examined: 



Museum National d'Histoire Naturelle, Paris (Paris Mus.). 

 Naturhistoriska Riksmuseet, Stockholm (Stockholm Mus.). 

 Zoologiska Museet, Kungl. Universitetet, Uppsala (Uppsala Mus.). 

 United States National Museum, Washington (U.S.N. M.). 



