GASTROPODA. 901 



!*.1|HOIO.I..... I ..rill. 1 



Tin- lateral \ iew .f a cast of this species given by Whitfield (op. cit., pi. VI, fig. 

 1:5 1 does not agree with our specimens, the outer thin! of the last volution being 

 niiirh fuller in the figure, and represented as convex or straight almost to the edge 

 of the aperture in-tead of deeply concave. Still, we cannot for a moment doubt 

 that \vi> have r. ally de-ril.ed the species intended by Prof. Whitfield, since the 

 inajiinty f them are from the locality which furnished the original types, and all 

 are precisely like specimens in the museum of the University of Wisconsin labelled 

 in I'rof. SVhittield's hand as Hiic.inix lutrlli. That the figure objected to may not 

 l>e true to nature is indicated liy the fact thatitdoes not agree with his fig. 12 which 



ated to be of the same specimen. It may be that the specimen is in part a 

 cast <>f the exterior, which would account also for the presence of the radiating 

 i -ilis. Not a trace of the latter is visible on any specimen seen by us that is truly a 



of the interior. 



The Mirface sculpture of S. fxpansn Hall sp., of the Trenton of New York, is not 

 well known. I nit casts of the interior are readily distinguished from those of this 

 -;';-. the volutions being less depressed, and subtriangular in section instead of 

 Milirenifonn. We have several fragments of a variety or closely related species from 

 the Black Kiver limestone of Kentucky, differing from the typical form of S. burlli, 

 BQ far as the imperfect material will admit of judgment, in having a thicker shell, 

 coarser surface markings, and smaller inner volutions when compared with the 

 expanded aperture which is fully as large as S. buelli. The aperture also is not so 

 abruptly turned outward dorsally. In the last feature it is more like S. expansa hut 

 the specimens are too small for that species and the volutions rounded on the back 



ad of subangular. Since the form is close to S. buelli we may designate it 

 provisional i nfucl.-ifrnsis. 



The M"'.-ii!-n represented by fig. 38 on plate LXV1I is considerably smaller 

 than any other of the species seen. The radiating ribs on the apertural 



uiMon al-u are stronger than they should be in S. buelli. If these differences 

 pro -ant in other specimens they should be distinguished as a variety at 



lout 



Formation and locality. In Minnesota .S. In* Hi is:i rare foMll and BO far known only from the lime- 

 stone* of the Stones Rh " -. Cannon Fall* and Old Conr-.r, I In Wisconsin, however. 

 It In nut uncommon and continue* Into th- overlying lime* tones of tin- Hlack River group; Belolt and 

 Janenvllle are the principal localities. In Illinois it ...-.-uni at Rock ton and I)|XTI. 



VoUettion*. Geological and Natural II ' mneoota; University of Wisconsin; Charles 



Schuchert; E. O. Ulrich; W. H. Soofleld. 



Mutmrn H'gifter, No*. 7293. 7318. ?&644. 



