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aiKt)''] PRO(n<:EDINGS OF TIIK NATIONAL MIISIUIM. 377 



a t'jicsiinih' of (lu^ lyi»', as lij^iniul )>y S(>\v(Ml)y, and ii|;aiii il has mow, 

 the appoaiaiico of a rartula than the characteristic aspecl of im.v. 



S|K'('iiiuMis closely a|;r(«(Mn<;- with Ivccvc's (ij^urc* arc^ in tlic National 

 colh'clion (Mus. JSIo. 1(MSL*'J); they were jiresented by tiic hitc Dr. Lea, 

 \\\m received tlieni, as \v<01 as other (5 alapa^os species, directly IVoni 

 Mr. Cninin^-, and wi're no donht a. part of the orij;inal lot, collected at 

 these islands by Cnininj;' iiiniscll", 



li. nuxis an e\ceedinj>ly variable lorin, and exhibits so many as))ects 

 of variation, that the most conservative^ c()n<'holoj»ist mif^ht easily be 

 led into si)ecies making, even with an abnndancc of individuals before 

 him, for this is on(^ of those ]>rotean forms, like, for instance, I'tdula 

 Ntri(/<>sa-C(H>prri- 11 ai/dcH i-J li'vtp/ti U i i- 1 (lali()cnsis etc., beIonj>in{if to the 

 (U'litral province of the United States,t that can not be jMop^Mly exem- 

 ]>lilied or nnderstood by a few examples, nor even by a. hundred speci- 

 mens. In B. mix, some individuals are ventricose, others rather slen- 

 der; in some the columella is straight or subarcuate, in others more or 

 less twisted, or more properly distorted. Often the callus <ni the body 

 whorl is heavy (u- thick, and connecting, forming- a peristome; occa- 

 sional individuals exhibit a tuberculoid thickening- of the i)arietal cal- 

 lus on its edj^e. In some instances the shells aie thin and almost 

 translucent, others again, and more frequently, are opacjue and solid. 

 The sculpture varies from simple longitudinal incremental striae more 

 or less conspicuous, that is to say, tinci or coarse, to exanlph^s with 

 transversely or spirally incised gi'ooving. Where these two aspects of 

 sculpture are present in the same individual, a more or less distinct 

 rectanjiular nmghening is the result. Tretpiently the ]nevailing <u>l()r 

 is whitish or dingy white, in others dull i)urplish brown; many inter- 

 mediate shades of these colors occur, and banded exami^Ies are not 

 uncommon; in these thebands are sometimes conspicuous and striking 

 and point, towards a. ])ossible if not |)r()bable greater eoIor-divt^rgeniM', 

 combined with sh'ndernessof form, suggesting ForhiiH^ ackafmeUinus. 



Taking into consideration the ditferent expressions of variation, 

 i. v., form, sculpture, color, ami general proportions, nuxX exhibits 

 th(^ greatest versatility; tln^ extent of varial)ility illustrated in the 

 numerous exanii»les, about two hundred betbre me, wainmts the 

 assumption that ten times the number would furnish many other 

 facies, if not extiemes ol variation. 1 have above calh^l attention 

 to the discr«'pancies, between the tlgun^s of Soweiby and Keeve. In 

 all cases where the various Galapagos s])ecies described by Broderii) 

 and Sowerby are refi^ried to, the lat ter's liguies must be regarded as 

 authoritative, and be re<'ognized as the standard type. Keeve's 

 tigures are fre(iu(Mitly, if not usually, not, a facsimile of the original, 



' It is goinvrally uudeiHtood that Ktiovo's great work Ih in the inaiu, buHod upon, 

 iuid ilhiHtratoH the ('uniing (•onc(!ti()n. 



tHiiiiicy'N Mamiiil Am. Liiiid Sluills, ji. U\\\. 



t li. mix occurs on thrco of tlio iHJaud.s, viz, (JliarluH, Chtithiim, and Alli«nnarlt'. 



