1066 THE PAELONTOLOGY OF MINNESOTA. 



[Holopea simills. 

 HOLOPEA 8IMILIS, H. Sp. 

 PLATE LXXIX, FIG. 26 



This shell might be described as a miniature H. ampla, were it not that its apical whorls rise higher 

 above the last two, giving it a somewhat acute apex. Comparing it with young examples of that species 

 we find that it has more slender whorls, a higher spire and smoother shell. There is a moderately wide 

 umbilical depression in the base but the perforation is very small, the suture is distinct and sometimes 

 slightly channelled, at other times the top of the whorls is merely flattened; the mouth is rounded and 

 oblique, the exterior surface marked by fine lines of growth which curve rather strongly backward in 

 crossing the whorls from the suture. The specimen figured is above the average in size. 



At first we thought this species might be the same as Hall's H. obliqua, but after repeated and 

 always fruitless efforts to identify that shell we have decided to give it a new name. 



Formation and locality. Ctenodonta bed of the shales of the Black River group, Minneapolis and 

 St. Paul; also at localities in Goodhue and Fillmore counties. A similar form, but having a larger umbil- 

 icus, occurs In the Fusispira bed near Cannon Falls. We have also a specimen from the Lorraine group 

 at Covlngton, Kentucky, which seems to agree exactly with the Black River form of the species. 



Collections. Geological and Natural History Survey of Minnesota; E. O. Ulrich. 

 Museum Register, No. 7381. 



HOLOPEA ROTUNDA, n. sp. 



PLATE LXXIX, FIGS. 20 and 21. 



Shell thin, of medium to rather large size, with hight and width about equal, consisting of about 

 four rather rapidly enlarging, strongly convex, ventricose whorls; umbilical perforation extremely small, 

 probably closed in some specimens; 'suture distinct, sometimes faintly canaliculate on the last whorl; 

 aperture somewhat oblique, subelliptical, the hight exceeding the width by about one-seventh; inner lip 

 thin, curved, the edge reflected so as to almost cover the umbilical perforation; surface with obscure lines 

 and an occasional faint wrinkle crossing the whorls from the suture with a slight backward direction. 



The spire is not so high and the whorls more ventricose than in our H. excelna and H. concinnula, 

 while the umbilicus also is smaller and the aperture more oblique than in the latter. H. similis has less 

 uniformly convex whorls and more of an umbilicus, while H. paludiniformis Hall seems to have a higher 

 spire and to differ in other respects. 



Formation and locality. Stones River group, Dixon, Illinois; Trenton group, Hartsville, Tennessee. 

 Collection. E. O. Ulrich. 



HOLOPEA CONCINNULA, n. sp. 



PLATE LXXIX, FIG. 6. 



Hight about 24 mm., width 18 mm., apical angle 72. Volutions about five, rounded, with a barely 

 perceptible angularity near the middle of the upper part shown in casts of the interior; umbilicus small; 

 very faint undulations and lines of growth, crossing the whorls almost vertically, may be seen on the 



last whorl. 



Of this species we have seen only the cast of the interior figured on plate LXXIX. In its form it 

 resembles H. paludiniformis Hall, a Trenton limestone shell in New York, very closely, yet we are fully 

 satisfied that it will prove quite distinct. At present the possession of an umbilical perforation by our 

 species is the only differential feature that our limited knowledge of the New York shell permits us to 

 mention. 



Formation and locality Stones River group, Beloit, Wisconsin. 

 Collection. University of Wisconsin. 



