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The famil>-('atastomitlac (suckers) is among the bestknown and most easily recognized of the fresh-water fishes. They are cliara(~terizeC1 11)the prcsence of a protractile mouth, fieshp, sucker-like lips, aiid toothless jaws, tlie mouth being protrusible to a greater extent tliaii iii other fishes.'I'hey are bottom feeders, liviiig chiefly upon vegetation, smaller Nollusea, Entomostraca, worms, larvae of aquatic iiisects, eggs of various kinds, aiid mud, wliicli they doubtless ingest f o r the organic matter it coiitaiiis. 111 tlie act of fcccling, the mouth is drawn tlownward aiitl foi-w\-artl from the uiiderside of tlie head like a spout. Food is taken into the mouth by sucticm, t o 11-hicli tlieiy protractile months a i d fleshy lips are peculiarly adapted. According to Konleiigcr ( '04), "tlic sliape, size and character of the mouth aiitl jaws, tlie extciit to which they can protrude and retract largely depend upon cliffcrciices of liabit and f oocl. ' ' A review of tlic literature has rerealed iiotliiiig relative to the details of the modus opcraiidi of the protrusible mouth of tlic Catastomithe beyolid what is geiicrally recognized for fishes with protractile premaxillaries.At the suggestion of T'rof. Raymond C. Oshrii, tlie writer niidertook a study of the anatomy of the jaws and methods of feeding of tlie Catastomiclae in order t o determine the factors irivolved in the chai-acteristic protrusion of the mouth. 2.57

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