72 NEW YORK STATE MUSEUM 



a more precise definition of the characters of the species than could be 

 given by its author. 



Diagnosis. Shell of medium size, turbinate conic, a little higher than 

 broad ; spire elevated, hight greater than the basal diameter of the body 

 whorl ; apical angle 60, base imperforate (?) ; suture deeply impressed, 

 increasing outward in obliquity ; earlier whorls overlapped by the later for 

 one half the interval between the slit band and the base ; volutions about 

 five, subangular, slit band narrow with elevated margins, at or just above 

 the middle of the whorl. The body whorl has a gently convex, almost 

 direct slope from the suture to the slit band, but is convex and subventri- 

 cose below the periphery. On the earlier whorls the depression of the 

 upper surface is more pronounced, and the concavity is divided by a sharply 

 developed keel or single ridge. A narrow, rather obscure and nearly vertical 

 band runs along the suture. Surface marked by fine, irregularly concentric 

 lines which cross the carina without interruption but are directed backward 

 and are caught up at the slit band. On casts the carina and the slit band 

 are indicated by rather low, rounded ridges. 



Aperture unknown. 



Observations. The angularity and prominence of the whorls in this 

 species show its close approach to forms of Murchisonia having the expres- 

 sion of M. hespelerensis Whiteaves, and in this respect it is in har- 

 mony with Pleurotomaria durhamensis, these two species 

 differing chiefly in the degree of elevation of the spire. 



Besides the larger specimens from Rochester six smaller ones were 

 obtained from the lower Shelby layer, and these distinctly exhibit the keel 

 of the upper side of the whorl and the spiral elevated lines of the slit 

 band. The upper Shelby dolomite has furnished no examples of the 

 species. 



HORMOTOMA SaltCr. 1859 



Hormotoma whiteavesi sp. nov. 



Plate 8, fig. 5-9 



Shell long, slender, terete and acuminate, its entire length being 

 nearly four times the diameter of the body whorl. Apical angle- i8-2O. 



