FIG. 138.—California Sucker, _Catostomus occidentalis_ Agassiz. (Photograph by Cloudsley Rutter.) ] =Fossil Cyprinidæ.=—Fossil _Cyprinidæ_, closely related to existing forms, are found in abundance in fresh-water deposits of the Tertiary, but rarely if ever earlier than the Miocene. _Cyprinus_ _priscus_ occurs in the Miocene of Germany, perhaps showing that Germany was the original home of the so-called "German carp," afterwards actually imported to Germany from China. Some specimens referred to _Barbus_, _Tinca_, _Rhodeus_, _Aspius_, and _Gobio_ are found in regions now inhabited by these genera, and many species are referred to the great genus _Leuciscus_, _Leuciscus œningensis_ from the Miocene of Germany being perhaps the best known. Several species of _Leuciscus_ or related genera are found in the Rocky Mountain region. Among these is the recently described _Leuciscus turneri_. [Illustration: FIG. 139.—Pharyngeal teeth of Oregon Sucker, _Catostomus macrocheilus_. ] Fossil _Catostomidæ_ are very few and chiefly referred to the genus _Amyzon_, supposed to be allied to _Erimyzon_, but with a longer dorsal. _Amyzon commune_ and other species are found in the Rocky Mountains, especially in the Miocene of the South Park in Colorado and the Eocene of Wyoming. Two or three species of _Catostomus_, known by their skulls, are found in the Pliocene of Idaho. [Illustration: FIG. 140.—Razor-back Sucker, _Xyrauchen cypho_ (Lockington). Green River, Utah. ] =The Loaches.=—The _Cobitidæ_, or loaches, are small fishes, all less than a foot in length, inhabiting streams and ponds of Europe and Asia. In structure they are not very different from minnows, but they are rather eel-like in form, and the numerous long barbels about the mouth strongly suggest affinity with the catfishes. The scales are small, the pharyngeal teeth few, and the air-bladder, as in most small catfishes, enclosed in a capsule. The loaches are all bottom fishes of dark colors, tenacious of life, feeding on insects and worms. The species often bury themselves in mud and sand. They lie quiet on the bottom and move very quickly when disturbed much after the manner of darters and gobies. Species of _Cobitis_ and _Misgurnus_ are widely distributed from England to Japan. _Nemachilus barbatulus_ is the commonest European species. _Cobitis tænia_ is found, almost unchanged, from England to the streams of Japan. Remains of fossil loaches, mostly indistinguishable from _Cobitis_, occur in the Miocene and more recent rocks. From ancestors of loaches or other degraded _Cyprinidæ_ we may trace the descent of the catfishes. The _Homalopteridæ_ are small loaches in the mountain streams of the East Indies. They have no air-bladder and the number of pharyngeal teeth (10 to 16) is greater than in the loaches, carp, or minnows. CHAPTER IX THE NEMATOGNATHI, OR CATFISHES