16 THE NAUTILUS. 



of No. 1. The others are well differentiated, yet closely related. 

 No. 1 is the most abundant in numbers ; the others are apparently 



rare. 



NOTES ON EASTERN AMERICAN ANCYLI. II. 



BY BKYANT WALKER. 



In preparing my former paper on this subject (NAUT., XVII, p. 

 13), I overlooked Hedley's note on Ancylastrum (Proc. Mai. Soc., 

 I, p. 118) in which he calls attention to the fact that Bourguignat's 

 type was A. cumingianus and not A.fluviatilis. The latter species 

 being the type of the genus Ancylus, Ancylastrum, as used by Cles- 

 sin and those who have followed him, was wholly unnecessary, being 

 equivalent to Ancylus s. s. This rectification leaves the section re- 

 presented by A.fluviatilis and characterized by its elevated, capuli- 

 form shell, with the apex recurved and decidedly posterior, free, as 

 it should be, to be known as Ancylus s. s. 



The division of the Eastern American species into two sections 

 distinguished by the character of the apex, was only a further step 

 in the direction pointed out by Clessin in establishing his section 

 Haldemania and, had his name been available, it would have been 

 used for one of them. Independent of the apical characters, Cles- 

 sin's group was a valid one, and he was entirely justified in separ- 

 ating it from the Eurasion sections represented respectively by A. 

 fluviatilis and lacustris. And the fact that both of these species 

 have the apex radiately striate, does not at all militate against the 

 validity of Clessin's Haldemania, nor of the two sections that have 

 been proposed to take its place. In order, however, that there may 

 be no confusion hereafter on this point, the description of the section, 

 which includes the Eastern American species with a striate apex, 

 may be amended to read as follows : 



Section Ferrissia Walker. 



Shell conical, ovate, oval or oblong, usually elevated ; apex acute 

 or somewhat obtuse, placed only slightly behind the middle of the 

 shell, and usually turned toward the right side, not recurved, radially 

 striate. 



Type : A. rivularis Say. 



Most of the species belonging to this section are by preference in- 



