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 rei>resentative of the preceding, if not 

 identical with it. Birge mentions minute striae in the meshes. P. 

 stramineus is said to be lower than P. hastatus, while its beak is shorter. 

 Undoubted specimens of P. dentieulatus 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. E. Mueller's Plate IV, Fig. 18, with the 

 outline given by Birge at Plate II, Fig. 11. The color in both is deep» 

 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. 



Pleuroxus trigonellus O. F. Miiller. 



Lynceus irigonellus — O. F. Miiller, Lievin, Lilljeborg, Leydig, Fric. 

 ? Pleuroxus ornatus — Schoedler. 



Dorsal line strongly arched; the beak rather long, straightish, 

 pigment fleck smaller than the eye. 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 Grepidocercus, 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 aduuctus Jurine. 



Monoculus aduncius — Jurine. 



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. bairdil and P. dentieulatus 

 Birge) are very nearly related. The ephippium, where known, is 

 marked by minute punctation and a darker color. 



