GASTROPODA. 1065 
Holopea insignis.] 
HoLoPEA INSIGNIS, ”. Sp. 
PLATE LXXIX, FIGS, 1—5. 
Shell thin, attaining a width of 40 mm.; average width about 32 mm.; hight about 28 mm.; hight in 
young examples relatively greater, nearly or quite equalling the width; spire low; volutions about four, 
casts of the interior usually consisting of two or two and a half, very rapidly expanding, ventricose, the 
vertical diameter greater than the transverse, subelliptical in cross-section, narrowly rounded above so as 
to form a deeply impressed suture, and perhaps even more abruptly rounded on the under side where the 
contour enters a small but distinct umbilical perforation; mouth very moderately oblique, subelliptical; 
inner lip thin, produced so that it turns partly around the umbilicus; exterior surface marked by rather 
regular lines, generally less than a mm. apart, crossing 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 surfaceof good specimens, but on casts of the interior faint 
impressions of the wrinkles of growth only are visible. 
This fine species is distinguished from most of its congeners by its low spire, relatively high and 
rapidly expanding volutions, and deeply impressed suture. 
Formation and locality.—Stones River group, Minneapolis, Cannon Falls and Faribault, Minnesota. 
Collections.—Geological and Natural History Survey of Minnesota ; EH. O. Ulrich; W. H. Scofield. 
Museum Register, Nos. 5042, 5554. 
HoLopEA APPRESSA, ”. Sp. 
PLATE LXXIX, FIGS. 7—10. 
This resembles H. insignis but has more slender whorls, a wider umbilical slope, more oblique and 
differently shaped aperture and more abruptly impressed suture. The whorls also are not nearly so full 
in the upper part of the outer side. 
Formation and locality.—Clitambonites bed of the Trenton group, Goodhue county, Minnesota. A 
variety with more convex whorls occurs in the lower part of the Trenton group at Burgin, Kentucky. 
Collections.—Geological and Natural History Survey of Minnesota; EH. O. Ulrich. 
Museum Register, No. 6765. 
HoLopea AMPLA, . sp. 
PLATE LXXIX, FIGS. 22—25. 
This is a large shell resembling in many respects both H. insignis and H. appressa. The spire is low 
but rises higher than in either of those species, the suture is less deeply impressed, the whorls on the 
whole more rounded in section and the surface undulations stronger. From the former it differs in addi- 
tion in having a wider umbilicus and more oblique aperture, and from the latter in having the whorls 
much less sharply rounded on the upper side. H. similis is a smaller species and has a smoother surface. 
Formation and locality.—Stones River group, Cannon Falls, Minnesota; Mineral Point and Beloit, 
Wisconsin. The Wisconsin specimens are smaller than those from Minnesota. 
Collections.—Geological and Natural History Survey of Minnesota; University of Wisconsin; BE. O. 
Ulrich; W. H. Scofield. 
Museum Register, Nos. 5836, 7355. 
