904 NEW YORK STATE MUSEUM 



of the way to the beak. The dorsal valve has a low fold in 

 the middle with eight ribs on each side. The median fold is 

 grooved down the middle from near the beak. The resemblance 

 of this mutation to the normal S. granulosus is striking, 

 specially in the presence of the groove in the median fold, which 

 in old individuals of the normal type dies out toward the 

 margin. 



Localities. Abundant at Canandaigua lake, Livonia salt shaft 

 and all the Moscow localities. Total specimens 55. 



Spirifer marcyi Hall, mut. pygmaeus no v. 



Plate 3, fig. 5, 6 



This is a large, broadly oval form, with rounded cardinal 

 extremities. It measures 4 mm in width and 2 mm in hight. 

 The hinge line is curved and reaches nearly to the extremities. 

 The dorsal valve has a broad low median fold, reaching two 

 thirds of the way to the beak. The six ribs on either side are 

 rounded and wider than the intervening furrows. 



Locality. A single specimen from the Livonia salt shaft. 



Genus cyrtina Davidson 

 Cyrtina hamiltonensis Hall, mut. pyginaea nov. 



Plate 3, fig. 16 



The single specimen of this shell observed is a dorsal valve, 

 3 mm broad and 1% mm in length. The median fold is broad 

 and moderately high, with three wide folds on either side of 

 it. The surface is highly punctate. The shell is in all respects 

 an immature phase of the Hamilton species to which it is 

 referred. 



Locality. Canandaigua lake. 



Genus nucleospira Hall 

 Nucleospira concinna Hall, mut. pygmaea nov. 



Plate 1, fig. 4; plate 2, fig. 5 



This form is almost circular in outline, the valves slightly 

 and equally convex, beaks small and incurved. The size is 1 

 mm in length, 1% mm in breadth, and % mm i n thickness. The 

 valves are internal casts, but indicate a smooth surface. The 

 ventral valve is unmarked; the dorsal has a slight depression 



