CONTRIBUTIONS TO PALiEONTOLOGY. 51 



This minute species has a length of about a quarter of an inch, and pos- 

 sesses in some degree the character of the species last described ; but the 

 volutions are more angular and the suture-line more deeply impressed, while 

 the concentric striae and the spiral band are proportionally much stronger. 

 Six specimens have been examined. 



Geological formation and locality. In the Hamilton group. 



GENUS LOXONEMA (Phillips). 



In the Schoharie grit, and in the limestones above this rock, there are 

 numerous casts, which, though evidently belonging to different species of 

 LoxoNEMA or MuRCHisoNiA, Cannot readily be distinguished in the absence 

 of surface-markings. Several species of these genera have already been de- 

 scribed (14th Regents' Report, pp. 103, 104), from specimens retaining the 

 surface-markings. There are other forms still, which, although we have no 

 specimens with the shell preserved, nevertheless differ so widely from the 

 others as to be distinguished by the form and proportions of the casts. 



One of these from the Schoharie grit has the form and proportions of L. 

 attenuata of the Upper Pentamerus limestone ; and in the casts, no means 

 exist of pointing out characters which will distinguish the one from the other. 

 Other specimens resemble the L. coinpacta; but a careful comparison shows 

 the volutions to be a little more rotund, and the spire more rapidly ascending. 

 The determination of species in this condition is attended with many difficul- 

 ties, 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 ventured to characterize two or three 

 species among the specimens which occur in the condition of casts. 



LOXONEMA SOLIDA (n.s.). // J^ U^. 6, 

 Shell turritiform, elongate. Spire gradually ascending : volutions 

 moderately convex, the height of each one about half the dia- 

 meter of the spire at the same point. 



In a specimen of moderate size, five volutions from near the base 

 measure one inch in vertical height. 



This species is intermediate between L. com'pacta and L. ohtusa in pro- 

 portions of spire, and the volutions are slightly more convex. The specimens 

 are all imperfect, without the shell, and are only to be distinguished by the 

 form and proportions of the volutions. 



Geological formation and locality. In Schoharie grit : Schoharie. 



1861.] 



