124 THE NAUTILUS. 



In the synonymy of suhulare may be included Trypanostmna 

 pallidum Lea/ This is merely an extreme form, such as occurs 

 somewhat rarely among fresh-water Gastropoda. It represents 

 an old-age development, denied to all except a few animals of 

 unusual vitality or unusual good luck in escaping hardships 

 and enemies. Judging by the figure in Tryon ^ (the description 

 suggests difficulties) Melania tracta Anthony, placed by Tryon 

 in the synonymy of Pleurocera elevatum Say, is the pallidum 

 stage of suhulare growth. 



Pleurocera subidare is probably the most widely distributed 

 member of its genus, inhabiting from easternmost Ontario to 

 Minnesota, Kansas and Arkansas. East of the Mississippi it 

 does not appear to go below the line of the Ohio river. Con- 

 sidering the variableness of the family, the characteristics of 

 this species are remarkably constant. There is slight difference 

 between the suhulare of the Great Lakes region and that of 

 streams of northern Arkansas. 



The synonymy of this species may be set down as: 



Melania suhularis Lea, 1831. 



Melania tracta Anthony, 1850. 



Melania neglecta Anthony, 1854. 



Melania intensa Anthony mss. , Reeve, 1860. 



Trypanostoma pallidum Lea, 1862. 



Trypanostom,a labiatum Lea, 1862. 



A NEW HOLOSPIRA FROM CHIHUAHUA. 



BY HENRY A. PILSBRY. 



HOLOSPIRA BRYANTWALKERI n. Sp. PI. 4, fig. 6. 



A species of the subgenus Haplocion. The shell is rimate, 

 cylindric, the upper third tapering, summit mucronate. Very 

 pale flesh-colored. Sculpture of closely set riblets, narrower 

 than their intervals, very straight and retractive on the upper, 



iProc. Acad. Nat. Sci., p. 173; 1862. 



* Monograph of Sir epomatidae, Washington, p. 96; 1873. 



