ENTOMOSTRACA OF MINNESOTA. 255 
with small teeth; claw with two basal spines. Color corneous. The 
sculpture consists of faint reticulations. The ephippium forms a 
truncation of the upper part of the shell. Length 0.50 to 0.55 mm. 
The male has a shorter beak; the first foot has a weak hook; and the 
Spermatozoa are spherical. 
Pleuroxus stramineus Birge. 
This form is the American representative of the preceding, if not 
identical with it. Birge mentions minute strie in the meshes. P. 
stramineus is said to be lower than P. hastatus, while its beak is shorter. 
Undoubted specimens of P. denticulatus exhibit the same differences, 
an increase in the convexity of the shell accompanying an increase 
in the length of beak. The form of the abdomen appears nearly 
identical, if we compare P. HE. Mueller’s Plate IV, Fig. 18, with the 
outline given by Birge at Plate II, Fig. 11. The color in both is deeps 
especially during the period when the winter egg is forming. The 
direction of the reticulations is said to differ, but P. E. Mueller’s 
figure does not furnish positive evidence of this. Length 0.6 mm. 
~leuroxus trigonellus O. F. Miiller. 
Lynceus trigonellus—O. F. Miller, Lievin, Lilljeborg, Leydig, Fric. 
? Pleuroxus ornatus—Schoedler. 
Dorsal line strongly arched; the beak rather long, straightish, 
pigment fleck smaller than theeye. Shell faintly reticulate, the mark- 
ings consisting of transparent ridges. Post-abdomen widest in the 
middle, attenuated slightly toward the end, which is truncate; claw 
large, with one long and one very small basal spine. The anal 
margin of the post-abdomen has a series of small spines, and the lower 
shell-margin is hairy. The post-abdomen of the male is somewhat as 
in Orepidocercus, and densely hairy; the first foot has a moderate 
hook. 
To judge from Kurz’s statements, P. ornatus Schoedler is not 
specifically distinct. Not yet identified in America. 
Pleuroxus adunctus Jurine. 
Monoculus adunctus—J urine. 
Very like P. trigonellus, but with the back more strongly arched. 
‘The anterior part of the shell is striped. The beak is shorter than in 
P. trigonellus, but no other permanent differences are discoverable. The 
temptation to believe this a mere varietal form of P. trigonellus is great. 
Indeed, four species (the two here noted, P. bairdii and P. denticulatus 
Birge) are very nearly related. The ephippium, where known, is 
marked by minute punctation and a darker color. 
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