FOSSILS OF THE SILURIAN AND DEVONIAN ROCKS. 169 



tricose ; spire depressed below the upper side of the body-whorl. Aperture 

 very large and circular ; inner lip usually in contact with the spire, so as to 

 leave a moderately large umbilical cavity. Surface traversed by fine striae, 

 and near the aperture coarser, somewhat undulated lines of growth, crossed by 

 faint traces of extremely fine, revolving lines. General size differs in different 

 individuals ; the illustration shows a specimen of average size. 



Formation and Locality. Found in the Corniferous limestone of the Devonian formation in 

 Jefferson county, Ky., and in Clark county, Ind. 



D'Archiac and DeVemeuil. 



Murchisonia, D'Archiac and Verneuil. Bull. Soc. Geol. Fr., Vol. 12 1841. 

 Etymology : Named after Sir R. I. Hurchison, of England. 



This genus was proposed by D'Archiac and De Verneuil, to include Buccin- 

 uni spinosum and B. abbreviatum of Sowerby, Turritella bilineata of Gfoldfuss, 

 and others. Shells spiral, with very elevated spire and many volutions, 

 marked by a spiral band and bent striae; body very elongate, with a notch or 

 slit in the outer lip of the aperture, or where this is wanting, the striae are 

 bent, indicating the slit. Murchisonia are a sort of elongate Pleurotomaria. 

 Type, Murchisonia bilineata. 



Murchisonia desiderata. HALL. 



Plate XXVI., figure 8. 



Murchisonia desiderata, Hall. Descpt. of New Sp. of Foss. 1861. 

 Murchisonia desiderata, Hall. 15th Rep. N. Y. St. Cab. 1862. 

 Murchisonia desiderata, Hall. Pal. N. Y., Vol. 5, pt. 2, p. 891885. 



Shell elongate, turretiform ; spire somewhat rapidly ascending. Volutions 

 ten or more, and obtusely angular, flattened on their upper sides, and a little 

 more convex below the spiral band. The volutions, from apex to aperture, are 

 gradually enlarging. The greatest width of the last volution is about equal 

 to the combined height of the second and third whorls, but scarcely more ven- 

 tricose than the preceding one, except towards the aperture. Aperture some- 

 what elongate ; the columellar lip thickened and bounded by a well-marked 

 callosity. 



Surface marked by distinct, concentric striae, which are sometimes raised 

 into fascicles above the general surface of the shell, and, bending gently back 

 from the suture, reach the spiral band, crossing which, they bend forward more 

 abruptly, making a gentle curve to the suture below. The spiral band, at about 

 three-fifths of the width of the volution below the suture, is simple, flattened 

 or slightly concave, limited by narrow, moderately elevated revolving lines, 



GEOL. SUK. 22 



