1068 THE PALEONTOLOGY Of MINNESOTA. 



LHolopea supraplana. 



section; suture distinct, very slightly canaliculate; umbilicus large, equalling about one-fourth of the 

 diameter of the shell; aperture moderately oblique, rounded, slightly modified above by the preceding 

 whorl; surface with very fine, obscure lines of growth and on the latter half of the body whorl a number of 

 more or less obscure undulations running parallel with the apertural margin. 



This shell resembles the inner whorls of H. pyrene, but its whorls seem to be proportionally more 

 slender and more nearly circular in section. Though small, the specimens are evidently mature. 



Formation and locality. Upper part of Trenton group, near Burgin, Kentucky. 

 Collection. -E. O. Ulrich. 



HOLOPEA SUPRAPLANA, M. Sp. 

 PLATE LXXIX, FIGS. 27 and 28. 



Excepting that the whorls increase more rapidly in bight, the general appearance of this shell, 

 especially in dorsal and ventral views, is greatly like H. insignis. However, in viewing the upper side, a 

 marked difference will at once strike the observer. The upper side of the whorls, namely, instead of being 

 rounded as in that species, is a sharply defined flat plane sloping gently downward to the suture and 

 extending outward about half the width of the body whorl, as seen in the apical view. The spire is low, 

 the outer side of the body whorl moderately convex, the base turning sharply into a small but, undeniable 

 umbilicus; inner lip very thin, reflected so as to form asemitubular prolongation from the umbilicus; 

 aperture very little, if at all oblique; surface markings, excepting a few obscure vertical lines near the 

 mouth, unknown. 



We know of two other species of this type, one from the upper Trenton at Nashville, Tennessee, in 

 which the upper plane is less sharply defined, the spire a little higher, and the umbilicus very small ; the 

 other from the Kichmond group at Richmond, Indiana, and Oxford, Ohio, having the upper plane fully as 

 well defined and wide, but not sloping downward, and the umbilicus much smaller or closed. In the 

 latter the sutural edge of the plane is raised.* 



formation and locality. Lower half of Fusispira bed, Trenton group, Kenyon, Minnesota. 

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

 Museum Register, No. 7493. 



Family CAPULID^E. 

 Genus PLATYCERAS, Conrad. 



This genus is only provisionally employed for the following two capuloid shells, 

 and as it includes a host of wonderfully diverse shells, upon which the opinions of 

 paleontologists vary greatly, we have thought it best to use the genus without 

 attempting to give either the synonomy or a diagnosis. 



PLATYCEBAS (?) WI8CON8INEN8IS, . sp. 



PLATE LXI, FIGS. 49-54. 



Shell rather small, capuloid, obliquely subconical, with the hight and width nearly equal; apex 

 obtuse, not spiral, turned slightly to the right or the left, and situated immediately over or curving 

 slightly beyond the apertural margin; aperture more or less obliquely rounded-quadrate, or broadly 

 subovate, the peristome horizontal or irregularly sinuate. Surface of cast smooth or with a few obscure 



As these ara both interesting and Important species and easily recognized, I propose to call the first Holopen mih- 

 vOfetuU snd the second Holapea orfordeiuit. E. O. ULKICH. 



