912 



NEW YORK STATE MUSEUM 



and the ancestral form is also extremely variable. There is 

 great variability in the size of the individuals, some being % 

 mm in diameter, others as much as 10 mm; but all have the 

 characteristic form. It occurs in moderate abundance in all 

 the localities. Canandaigua lake, Livonia salt shaft, Greigs- 

 ville and Moscow. Total specimens 28. 



Genus macbochllina Bayle 

 Macrochilina hebe Hall, mut. pygmaea nov. 



Plate 4, fig. 4 



The form i« conical, about twice as high as wide. The speci- 

 men illustrated has four and one half complete whorls, the top 

 being lost. The whorls are ventricose and the form slender. 

 It measures as it stands \M> mm in hight and* 1 mm in diameter. 

 This resembles the slenderer forms as they occur in the shale 

 There are two specimens of this species, from near the Dela 

 ware, Lackawanna and Western Kailroad at Moscow. They 

 are one fifteenth normal size. 



Macrochilina hamiltoniae Hall, mut. pygmaea Clarke 



Plate 4, fig. 1 



This species presents a shorter cone, the hight being about 

 half again as great as the diameter. The spire is short, having 

 but three whorls, the last whorl being ventricose and making 

 about three fourths of the full hight of the shell. The apei 

 ture is oval, higher than broad, acute above and obtuse below. 

 The mutation is an almost exact miniature of the ancestral M. 

 primaevus from the Schoharie grit. It measures 1*4 mm 

 in hight and % mm in diameter. It occurs at Oanandaigun 

 lake and the Livonia salt shaft. Total specimens 8. 



Genus pleurotomaria Def ranee 

 Pleurotomaria capillaria Conrad, mut. pygmaea nov. 



Plate 4, fig. 6 



This species is represented by several fragmentary speci 

 mens. It is a low cone, the whorls being ventricose an<] 

 rounded. On the upper part of each whorl are three to four 

 revolving grooves, separated by intervening carinae. Thf* 

 hight of am average shell is 5 mm, while the thickness is the 



