GASTEROPODA. 
39 
Pleurotomaria. This feature is not observed on the last volution, which is 
marked on one specimen by a faint carination near the upper part; on the 
lower side of the volution are four or five revolving carinate bands. 
The features preserved are altogether like those of Cyclonema, and in the 
absence of other evidence, it is thus referred. 
Formation and locality. In a calcareous band of the Chemung group at 
Nichols, Tioga county, N. Y. 
LOXONEMA, Phillips. 
In the Schoharie grit, and in the limestones above this rock, there are 
numerous casts of spiral univalves, which, though evidently belonging to 
forms like Loxonema or Murchisonia, cannot readily be distinguished in the 
absence of surface markings. Several species of these genera have been 
described ( Fourteenth Report on the N. Y. State Cabinet Nat. Hist.) from specimens 
retaining the external characters. There are other forms still, which, although 
we have no examples with the shells preserved, nevertheless differ so widely 
in their form and proportions from those already described as to be distin¬ 
guished by these characters alone. 
One of these from the Schoharie grit has nearly the form and propor¬ 
tions of L. attenuata of the Upper Pentamerus limestone, and in the casts no 
positive means exist of pointing out characters which will distinguish the one 
from the other. Specimens resembling the L. compacta, of the same geological 
formation, upon a careful comparison, show the volutions to be more rotund, 
and the spire more rapidly ascending. The determination of species in this 
condition is attended with many difficulties, and in the end there must still 
remain some doubt, when the differences of form and proportions may have 
been disguised by pressure or accident. Under these circumstances, I have 
characterized several species among the specimens which are only known in 
the condition of casts; leaving a more satisfactory determination to the future, 
and a collection of better specimens. 
