GASTEROPODA. 
89 
MURCHISONIA, de Verneuil and d’Archiac. 
Murchisonia desiderata. 
PLATE XXI, PIGS. 1-3. 
Murchisonia desiderata, Hall. Descriptions of New Species of Fossils, etc., p. 22. 1861. 
“ “ “ Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 50, pi. 4, fig. 12. 1862. 
Shell elongate, turretiform; spire somewhat rapidly ascending. Volutions 
ten or more obtusely angular, flattened on their upper sides, and a little 
more convex below the spiral band—the lower ones gradually enlarging; 
the greatest width of the last volution about equal to the height of the 
two above, and scarcely more ventricose than the preceding one, except 
towards the aperture. Aperture somewhat elongate; the columellar lip 
thickened, and bounded by a well marked callosity. 
Surface marked by distinct concentric strife, which are sometimes raised in 
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, and marked by the retrally curving strife, 
which are less prominent upon it and the adjacent parts than near the 
suture. Suture close. 
The height of five volutions from the mouth upward 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, as far as can be determined from the imperfect specimen. 
This species differs conspicuously from either of the two following forms in 
its proportionally greater length as well as the angularity of the volutions, and 
the distinct flattening upon their upper side. The suture-line is close, without 
indication of a groove, and the transverse strife are much less conspicuous 
than in the other species. 
12 
