The peculiar facility of the older entomologists, the fathers of the Sciences, for discarding each other's generic and specific names has in this instance, as in many others, given rise to be complicated synonymy, of which I give above that covering this extremely interesting little waterstrider. It is given more in detail in The Entomologist (London Eng.) for June, 1900, on Page 176, in which Kirkaldy elucidates it, relegating Say's specific name to synonymy, as it unfortunatley has been preoccuupied by Eschscholtz, who in 1822 described Hydrometra lineata from Manila, Philippine Islands. In the paper mentioned hereafter, Mr. J.O. Martin discusses the generic synonymy.