NORTH AMERICAN SPECIES OF BRANCHINECTA. 251 



are of about the same size, while B. Lindaldi is some- 

 what smaller. The body of B. coloradcnsis is not only larger 

 but more robust than that of B. Lindahli. The latter is much 

 more "fairy-like " in appearance, and specimens in formalin are 

 perfectly white or transparent. The color of B. coloradcnsis is 

 much more variable. It has not changed in formalin and varies 

 from creamy white to salmon. In the material collected July 

 29, 1904, were 26 males and 56 females ; the males were light 

 and the females were salmon without a single exception. But of 

 the 14 males and 26 females collected July 12, 1904, there 

 were several exceptions to this color distinction. 



Perhaps the most noticeable difference between B. Lindahli 

 and B. coloradensis is in the size and shape of the eye. (PI. I.; 

 13, 14, 15, 16). Packard (1883:338) describes the eyes of 

 B. coloradcnsis as "rather larger" than those of B. paludosa, 

 and the eyes of B. Lindahli as " rather large." A reference to 

 the table shows that the eyes of B. coloradensis are much larger 

 than those of B. Lindahli, the ratio derived from the average 

 measurements being for the males 1.67 to I and for the fe- 

 males 1.89 to i. It must be understood that, since the writer 

 has only 6 females of B. Lindahli the ratio for these may not 

 express as nearly the average as does the ratio for the males. 

 Verrill (1870 : 245) gives 0.66 mm. as the measurement of the 

 eye of the male of B. palndosa. This almost equals the small- 

 est measurements of B. coloradensis, but is considerably larger 

 than the largest measurements of B. Lindahli. In B. Lindahli 

 the ocular globe is developed but slightly better on the anterior 

 side than on the posterior side. In B. coloradensis, however, the 

 anterior side is developed much more than the posterior, or it 

 may be said that the eye is bent forward abruptly at the place 

 of union between the ocular globe and the peduncle. When 

 viewed from above, these eyes are very distinct from those of B. 

 Lindahli and can be distinguished at a glance. Although the 

 eyes of the female are somewhat smaller in each case than those 

 of the males, they are of the same form. Judging from Sars' 

 description (1896:44; PI. VI., Fig. 9; PL VII., Figs. I and 2) 

 the eyes of B, palndosa are more like those of B. Lindahli than 

 like those of B. coloradensis. 



