FAMILY rilYSID^ IO9 



Others have tried to propagate the view that Geoffroy's species was the 

 A. Jiuviatilis, their arguments cannot be said to outweigh the positive 

 statement of the original author. The first binomial author to use 

 Ancylus was Miiller, who must be credited with the genus. The name 

 Ancylastrum, published by Bourguignat (though probably suggested 

 by Moquin Tandon) was doubtless intended to be the equivalent of 

 Ancylus s. s., but the publishing author distinctly and repeatedly 

 announced the type to be Ancylus cutningiamis^ which differs in 

 many respects from typical Ancylus^ and will therefore retain the name, 

 which otherwise would have fallen into the synonymy of Ancylus s. s. 

 Acroloxus Beck, typified by A. lacustris Miiller, seems to be a well 

 characterized subdivision. Beck's first species was examined by Gray 

 and determined to be a Vclletia, which is an exact synonym of Acro- 

 loxus. Protancylus was proposed by the Sarasin brothers in iSyS, 

 for a form resembling Ancylus, from Celebes, but in which the gill is 

 fully developed. 



Typical Ancylus seems to be an Old World form, but Acroloxus is 

 represented in both hemispheres. The subdivisions of the typical sub- 

 genus so far recognized are as follows : 

 ? Brondelia Bourguignat, Rev. de Zool, p. 13, 1S62; Spic. Ivlal., 



xcv, Jan., 1S62, type B. drouetiana liourg., Algeria. 



This form, which is said to be an air-breather, a fact needing con- 

 firmation, is radiately ribbed and has a sinistral apex. ISfore informa- 

 tion about it is much needed, and it may prove to be an Acroloxus. 

 Lanx Clessin, Conch. Cab., ed. n, pt. 299, p. 10, iSSo ; type A. netv- 



bcrryi Lea, Oregon and California. 



The type has a smooth or concentrically striated apex, subcentrally 

 situated, obtuse ; the shell is larger and more solid than the majority 

 of the genus. A. fatelloides Lea, placed by Clessin with the above, 

 has a shell like A. 7ieivberryi, but more delicate, depressed, and with 

 a well marked radial system of coloration. 



The following groups are Nearctic or American ; Ferrissia is also 

 South African. 

 Z^-z'tT/i^x Walker, Nautilus, x\'ii, June, 1903, p. i;;: type ^«n'/?<5 



fuscus C. B. Adams. Chiefly lacustrine, with a smooth nepionic 



shell. 

 Ferrissia Walker, op. ciL. p. 15; type Ancylus rivularis Say. 



Chiefly fluviatile, with a radiately sculptured nepionic shell. 



The question as to whether Gundlac/iia is a distinct genus or merely 

 an exceptional second-season growth of Ancvlus, has been discussed 



