—— 
PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 
issued Ae 
SMITHSONIAN INSTITUTION 
U. S. NATIONAL MUSEUM 
Vol. 92 Washington: 1942 No. 3136 
A NEW SPECIES OF PHYLLOPOD CRUSTACEAN FROM THE 
SOUTHWESTERN SHORT-GRASS PRAIRIES 
By J. G. Mackin 
Arter several years of collecting streptocephalids in the Southern 
Plains regions of the United States, it has become apparent that some 
of the specimens do not conform with descriptions of Streptocephalus 
teranus Packard, to which species I have previously assigned all 
streptocephalids not having the peculiar spinous furcae of S. seal. 
I have in the past considered S. texanus rather variable. The study 
of a large number of specimens showed clearly that an undescribed 
species was present and that characters of all streptocephalids of our 
Plains region are quite constant. I am much indebted to my wife, 
Dorothy Louise Mackin, for the preparation of several hundreds of 
slides making possible the clear distinctions. I accordingly name the 
new species in her honor. 
Technique.—Two techniques were followed in these studies. The 
first consists of staining specimens with acid fuchsin and dissecting 
and mounting as usual in Canada balsam. The other method is one 
worked out to aid in the study of comparatively large parts and organs 
of these phyliopods, such as the claspmg antennae. Specimens are 
stained with acid fuchsin, with a few drops of hydrochloric acid added 
as usual, and then are run through the alcohols to benzene. A little 
Canada balsam is added to the benzene, and the specimens are then 
dissected. In dissecting for the clasping antennae, the head is cut 
off and then split along the sagittal plane, so that the two claspers are 
separated. The benzene is then allowed to evaporate slowly. If 
done gradually enough, distortion is eliminated. The balsam gives 
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