1016 THE PALEONTOLOGY OF MINNESOTA. 



[Honnotoma subangulata. 



Formation and locality. Var. angustata occurs rather rarely in the Vanuxemia bed of the Stones 

 River group at Cannon Falls, Minnesota, and in equivalent strata in Wisconsin, Illinois, Kentucky, Ten- 

 nessee, New Yo k and Canada; also in the shales of the Black River group at Minneapolis and near 

 Cannon Falls, and in the Utica group at Cincinnati, Ohio. The typical form is found from the Black" 

 River group on up to the top of the Richmond group at many localities. Good specimens occur in the 

 Maquoketa or Utica shales at Graf, Iowa. Var. sublaxa is so far known only from the Trenton group at 

 Auburn, Missouri, var. multivolvis in the Richmond group near Spring Valley, Minnesota, and var. yood- 

 huensis in the Phylloporina bed of the Black River group in Goodhue county, Minnesota. 



Colkctions. Geological and Natural History Survey of Minnesota; E. O. Ulrich; W. H. Scofleld. 

 Museum Register, No. 7337. 



HORMOTOMA SUBANGULATA, . Sp. 

 PLATE LXX, FIGS. 37-41. 



Length 20 to 30 mm., apical angle about 25, band flat, median in position on the angular whorls. 



The apical angle is wider and the volutions much more angular than in any of the varieties of H. 

 gracilis. The upper slope of the whorls is generally flat or very slightly convex, but occasionally it may 

 be a trifle concave. In none of nine specimens is the apical angle less than 24, and in one it is 26. The 

 two specimens represented on the same plate by figures 42 and 43 resemble this species in the angularity 

 of their whorls, but as the apical angle is only about 18 in these specimens it is perhaps advisable to 

 refer them provisionally to H. gracilis. (See preceding page.) 



Formation and locality. Ctenodonta bed of the Black River group, Chatfleld and near Cannon Falls, 

 Minnesota. At the latter locality a cast of the interior apparently of this species was found in the 

 Clitambonites bed of the Trenton group. 



Collection. E. O. Ulrich. 



HOKMOTOMA SALTEEI, n. Sp. (Ulrich.) 

 PLATE LXX, PIGS. 44-51. 



Murchisonia (Hormotoma) gracilis SALTER, 1859, Can. Org. Rem., Dec. 1, p. 22. (Not HALL'S species.) 



Hight 25 to 40 mm.; apical angle 20 to 24 in typical form (figs. 44-48), about 25 in var. canadensis and 

 20 in var. tennesseensis (flgs. 49-51) ; volutions nine or ten, rounded, more or less distinctly thickened above 

 at the suture and flat or concave just beneath ; band rather wide, flat or slightly concave, median in the 

 var. canadensis, a trifle beneath the center in the typical form and a little above the center in the var. 

 tennesseensis; lines of growth unequal, rather fine, never sharp. 



This is a larger shell and has a wider apical angle than H. gracilis. In the typical form the thick- 

 ening of the upper edge of the whorls is usually a well-marked feature, but it is less constant in both of 

 the Black River group varieties, and often wanting or quite inconspicuous in the Canadian form. Evi- 

 dently, the peculiarity increased with the evolution of the species. 



Another variety may be distinguished as var. nitida. This occurs rarely near the top of the Trenton 

 group in association with the typical form, from which, however, it is readily separated by its larger size, 

 relatively plump form and much wider apical angle. The latter is about 30, while the hight of a large 

 specimen was nearly 50 mm. The concavity beneath the suture is not very distinct on the lower two or 

 three whorls, but in all other respects their markings are precisely as in the typical form of the species. 



Formation and locality Var. canadensis occurs abundantly in the Black River rocks at Pauquettes 

 r qiids on the Ottawa river, and, more rarely, together with the var. tennesseensis, in equivalent or some- 

 what younger strata between Nashville and Lebanon, Tennessee. The typical form was found in abund- 

 ance, var. nitida rarely, in the upper part of the Trenton group between Burgin and Danville, Kentucky. 



Collection. E. O. Ulrich. 



