50 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



MURCHISONIA DESIDERATA ( n. s.). 4/^' ^^ 

 Shell elongate, turritiform. Spire somewhat rapidly ascending : 

 volutions ten or more, the five lower ones gradually enlarging, 

 and the last one scarcely more ventricose than the preceding; 

 flattened on the upper side, and a little more convex below the 

 spiral band. Aperture somewhat elongate; the columellar lip 

 thickened, and bounded by a well-marked callosity. 

 Surface marked by distinct concentric striae, which are raised in 

 fascicles above the general surface of the shell, and, bending 

 gently back from the suture, reach the spiral band, which is flat- 

 tened and limited by moderately elevated revolving lines. The 

 spiral band is slightly below the centre of the volution, and 

 marked by the retral curving striae, which are less prominent on 

 this and the adjacent parts than near the suture. Suture close. 

 The height of five volutions from the mouth upwards is nearly 

 two and a quarter inches, and the diameter of the last volution is 

 seven-eighths of an inch. The length of the aperture is about five- 

 eighths of an inch, and the width half an inch. 



This species occurs in the same rock with M. maia and M. leda^ and 

 differs conspicously from either of them in the proportionally greater length 

 of the volutions, and the distinct flattening upon the upper side. The suture- 

 line in the present species is close, without indication of a groove, while the 

 revolving striae are less distinct than in those species. 



Geological formation and locality. In Upper Helderberg or Corniferous 

 limestone : Falls of Ohio ; and probably among numerous casts of similar 

 forms in New-York. 



MURCHISONIA TURlilCULA ( n. s.). ^/ / /^ 

 Shell small, turritiform. Volutions about eight or nine, angular, 

 rapidly increasing from the apex, the last one not more ventricose 

 than the preceding, flattened above and a little convex below the 

 spiral band. Spiral band strongly elevated, distinctly bounded by 

 sharply carinated revolving lines, and below the centre of the 

 upper volutions. 

 Surface marked by strong elevated concentric striae above the band, 

 which are less conspicuous below it. Suture-line sharply marked 

 by the deep contraction of the shell : on the last voluion, the' 

 suture-line is continued in a slender spiral line beyond the margin 



of the lip. 



[August, 



