Report of the United States Geological Survey of the territories . ide-view of a cast of left valve, a space of inch ; beak very gibbons, prominent, narrowed, stronglyincurved, and directed a little forward, its point being immediately over theanterior margin. Surface of internal cast smooth over the gibbous umbonalregion, but showing traces of small, concentric undulations below the middle.(Right valve unknown.) Length, inches; height from base to hinge, inches; height totop of umbo, inches; convexity of left valve, inch. This shell has a more prominent, attenuated, a
Report of the United States Geological Survey of the territories . ide-view of a cast of left valve, a space of inch ; beak very gibbons, prominent, narrowed, stronglyincurved, and directed a little forward, its point being immediately over theanterior margin. Surface of internal cast smooth over the gibbous umbonalregion, but showing traces of small, concentric undulations below the middle.(Right valve unknown.) Length, inches; height from base to hinge, inches; height totop of umbo, inches; convexity of left valve, inch. This shell has a more prominent, attenuated, and strongly-incurved leftbeak than any other species of the Catillus group with which I amacquainted; being in this respect more like many species of typical Inoce-ramus, while its general form-places it with the former section. No speci-mens (if its right valve are yet known, but it is probably much less convexthan the left; I know of no other species with which it is liable to be con-founded. Locality and position.—Chippewa Point, Montana; Fort Benton GO UNITED STATES GEOLOGICAL SURVEY OF TEE TERRITORIES. liioniji iniis uudafoundiis, M. & H. Plate 3, figs. 2, a, tindabuvdue, Meek ami Hayden (1S62), Proceed. Acad. Nat. Sei. Pbilad., XIV, 26. Shell obliquely rhombic-subovate or subquadrate, gibbous; anteriorside very short, and rounding obliquely downward into the base; posteriorbasal extremity prominently rounded; posterior margin broadly rounded orsubtruncated; dorsal and anterior margin diverging from the beaks at anangle of about 90° ; hinge short; beaks moderately prominent and nearlyterminal, that of the left valve rather strongly incurved and directed obliquelyforward, while in the right it is straighter and less elevated; umbonal axisranging at an angle of about 70° to the hinge-line. Surface of both valves(in the condition of casts) ornamented by regular, strong, subangular, con-centric undulations, separated by wider, rounded depressions. Heig
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Keywords: ., bookcentury1800, bookdecade1870, bookpublisherwashi, bookyear1876
