The interesting new species of water-bug described below was received some time ago from Abbé P. A. Bégin, of Sherbrooke, Canada. It was captured swimming on a fresh-water stream some little distance above Sherbrooke, and is of more than ordinary interest, from the fact that it belongs to the genus Halobatopsis, Bianchi, a genus not yet recognized in the North American fauna, and only recently characterized, being based upon the South American Halobates platensis, Berg., also a fresh-water species.