Acipenser

[Lat. acipenser, a sturgeon.] (Zool.) A genus of fishes in the Linnsean system, the distinguishing characteristics of which are, that the mouth is retractile and destitute of teeth, and the gills have only one aperture on each side. The genus acipenser is separated by Aga iz from the other cartilaginous fishes. It forms a link between the o eous and cartilaginous fishes, having its gills protected by an operculum, and only a single i ue, or gill-opening, on each side of the respiratory currents: but at the same time having no rays to the branchiostegal membrane, and having the whole of its true internal skeleton in a cartilaginous state. By Cuvier, therefore, the genus acipenser is placed in the cartilaginous division of fishes, but separated from the rays, sharks, and lampreys, which have five or more gill-openings on each side, to form, along with the genera spatular i a and chimæra, the order eleuthero-branch i at a, or those which have the branch iæ free at their outer circumference. In the system of Aga iz the sturgeons are joined with the sauroid fishes, siluri, polypterus, and some other genera, to form the order Ganoides. See STURGEON. combinations from the others, it was found nece ary to employ three prefixes borrowed from the Greek; for example, hypo (under), hyper (above), or briefly per (in the highest degree.) Thus, hyposulphurous acid is an acid composed of sulphur and a smaller proportion of oxygen acid than sulphurous acid; perchloric acid contains more oxygen than chloric acid, . (For further details upon this subject, see CHEMICAL NOMENCLATURE.) The organic acids, which are much more numerous than the mineral acids, and which all contain carbon and hydro Acken, a town of Lower Saxony, in the duchy of Magdeburg, with a citadel, situate on the Elbe, about 5 miles from De au. Pop. 4,100.