356 MEXICA N BO UNDAR Y SHELLS— BALL. 



elongated forms strougly resembling the original Rhodea californica 

 and others of Stenof/i/ra like aspect which, in default of anatomical 

 details, were provisionally referred to MehinieUa. Later explorations 

 resulted in obtaining from the Sierra San Lazaro, about 25 miles north 

 of Cape St. Lucas, living specimens of BuUmulus artemcsia, W. G. 

 Binney, Columna ramentosaj Cooper, MelanieUa eiseniana, Cooper, and 

 Yitren indcntata, Say, examples of which were sent to me by Dr. Cooper 

 in order that their true relations might be determined by an examina- 

 tion of the anatomy. 



Eecent researches on the anatomy of the Ilelicidie by Ihering, Pils- 

 bry, Bedley, and others have shown conclusively that the external 

 moditications of the shell alone are not a sufficient guide to the genetic 

 relations of the animals concerned, and that under similar environ- 

 mental intluences the Helicidu', taken in a broad sense, of different 

 countries and different genetic history, produce strikingly similar modi- 

 fications of their shelly envelopes. These have hitherto naturally been 

 assumed to indicate a relationship which we now know does not exist. 

 Further, it appears that a more niinute scrutiny of the shells referred 

 to does in many cases reveal characters in them which, in the light of 

 our new information, point to their real aflfiuities, but which have hith- 

 erto been overlooked or regarded as of too little importance to be worth 

 dwelling upon. 



An examination of Dr. Cooper's shells affords striking confirmation 

 of the new views above referred to and shows that notwithstanding 

 superficial similarities the Californian and South American forms can 

 not be associated in the same nunor group and genetically are of dif- 

 ferent origin. I should state here that I considered in a recent paper 

 on the Bulimuli of Lower California' a number of the species collected 

 by the expeditions of the California Academy and forwarded to the 

 IS^ational Museum by Dr. Cooper in connection with a large series, includ- 

 ing most of the original types or author's specimens of species of this 

 group hitherto described from this region by Gould, Gabb, W. G. Binney,^ 

 and others. In his paper on " Land and fresh-water mollusks of Lower 

 California, ISIo. 4," Dr. Cooper, who had not had access to a series named 

 by me or to the original types above mentioned, ventured on some criti- 

 cisms of my work. These criticisms are almost wholly based on mis- 

 identifications of species or misconception of facts, and, in general, are 

 vitiated by these errors. I will mention only one instance, as I have no 

 desire to enter into controversy and prefer to allow the specimens, prop- 

 erly identified in the Museum series, to speak for themselves. Dr. 

 Cooper is under the impression that BnJimHliis p alJifli or ex\i>ts as a South 

 American si)ecies, and that Binney and Bland have described the den- 

 tition of Peruvian specimens.. Now, these authors specifically state 

 that their specimen was from Lower California, and it has long been 



> Proc. U. S. Nat. Mus., XVI, pp. 639-647, 1893. 

 2Proc. Cal. Acad. Sci., 2 ser., IV, pp. 130-143, 1894. 



