^TROPODA. 1 '"'"' 



lMlfBU.1 



II"1.0PKA IN8IONI8, N. Sp. 

 IM.A II I \\IX . I l< - 



Shell thin, attaining a width of -k) mm.; avera^' width about 32 mm.: night about 28 mm.; bight In 

 young examples relatively greater, nearly or quit* equalling the width: spire low; volutions about four, 

 casts of tli.- Int.-rior usually consisting of two or two and a half, very rapidly expanding, ventrlcose, the 

 viTdral diameter greater than the transverse, subelllptlcal In cross-section, narrowly rounded above M M 

 U> form a deeply Impressed suture, and perhaps even more abruptly rounded on the under aide where the 

 contour enters a small but distinct umbilical perforation; mouth very moderately oblique, subellfptlcal; 

 loner Up thin, produced so that It turns partly around the umbilicus; exterior surface marked by rather 

 regular lines, generally lew than a mm. apart, crowing the whorls from above almost vertically, a tend- 

 ency to turn slightly backward being apparent In most specimens; parallel with these, at Intervals 

 Increasing with age. numerous more or less obscure undulations; Indistinct revolving lines, one or two 

 mm. apart, may be observed on the outer surf ace of good specimens, but on casts of the Interior faint 

 Impressions of the wrinkles of growth only are visible. 



This One species Is distinguished from most of its congeners by Its low spire, relatively high and 

 rapidly expanding volutions, and deeply Impressed suture. 



Formation and toeaii/y. Stones River group, Minneapolis, Cannon Falls and Karibault, Minnesota. 

 CWI**wiw.-Geologlcal and Natural History Survey of Minnesota ; K. O. Ulrlcb; W. H. Scofleld. 

 JbruMMM Reyuttr, Nos. 6042, 5664. 



HoiXlt'KA A1TKK88A, H. Sp. 

 I'l.ATF. LXX1X. riOS. 7-10. 



This resembles fl. iiuiynu but has more slender wborls, a wider umbilical slope, more oblique and 

 differently shaped aperture and more abruptly Impressed suture. The wborls also are not nearly so full 

 in the upper part of the outer side. 



fomtation and locality. Clltanibonltes bed of the Trenton group, Goodhue county, Minnesota. A 

 variety with more convex whorls occurs In the lower part of the Trenton group at Gurgln, Kentucky. 

 CWiedAms. Geological and Natural History Survey of Minnesota; E. O. Ulrlch. 

 Muteitm Register, No. 6765. 



HOLOPKA AM PL A, fl. Sp. 

 PLATE LX.V.IX. KIOS. a-JS. 



This Is a large shell resembling In many respects both H. in$iynit and H. apprewa. The spire Is low 

 but risen higher than In those species, the suture Is less deeply Impressed, the whorls on the 



whole more rounded In section and the surface undulations stronger. From the form. -r It differs In addi- 

 tion In having a wider umbilicus and more oblique aperture, and from the latter In having the whorls 

 much lest sharply rounded on the upper side. //. rimilit Is a smaller species and has a smoother sn 



and loeaWty.-Stones River group. Cannon Kails. Minnesota; Mineral Point and Belolt, 

 Wisconsin. The Wisconsin specimens are smaller than those from Minnesota. 



OoUettfwu. -Geological and Natural History Survey of Minnesota; University of Wisconsin; K. O. 

 n: W. II Scodeld. 



Jftueum Kfffuter, Nos. 6880, 7366. 



