NORTH AMERICAN SPECIES OF THE GENUS ATAX 203 



form after being first shrivelled by being put into the mixture, 



Absolute alcohol 1-10 of the total volume, 



is recommended by Koenike (96) as an improvement over his 

 previous formula, and has been of late used in place of it, 

 without sufficient time having elapsed to judge of its merits. 



In the preparation of slide mounts, specimens are removed 

 from the preservative, thoroughly washed in distilled water, 

 treated with a dilute potassium hydrate solution, a rent made 

 in the skin and through it the contents of the body pressed out, 

 again thoroughly washed, passed through the grades of alcohol 

 and clearing mixture and finally mounted in balsam. By this 

 means a perfectly transparent mount is obtained and all the 

 hard parts are readily studied. There is more or less distor- 

 tion, but comparison with specimens preserved in other media 

 assists in obtaining a correct view of the relations of the hard 

 parts, which are themselves in perfect condition. The mouth- 

 parts are removed from the body, separated by dissection and 

 also mounted for detailed examination. 



The study of the material collected has resulted, as before 

 stated, in the detection of 13 species, of which 7 are new and 

 have been briefly described in a preliminary paper published in 

 the Zoological Bulletin for June, 1898. The list is as follows; 



1. Atax crassipes (Mliiler). 



2. Atax aculeai/us Koenike. 



3. Atax pecti/natus mihi. 



4. Atax intermedins Koenike. 



5. Atax abnormipes mihi. 



6. Atax indistinctm mihi. 



7. Atax serratus mihi. 



8. Atax fossulatus Koenike. 



9. Atax stricta mihi. 



10. Atax areuata mihi. 



11. Atax ypsilophorus (Bonz). 



12. Atax tumidus mihi. 



13. Atax (Najadicola) ingens (Koenike). 



In the arrangement of these species in the order given, an 

 attempt is made to preserve the sequence in which the Eu- 



