PAGE. 



HORMOTOMA SUBANGULATA U. and S 1016 



Cast of the interior, apparently of this species. Clitambonites bed of the Tren- 

 ton group, Cannon Falls, Minnesota. 



A small testiferous specimen from the Ctenodonta bed of the Black River group, 

 Goodhue county, Minnesota. 



Two views of a larger example. Ctenodonta bed at Chatfleld, Minnesota. 



Two whorls of the original of flg. 38, x2, showing band and surface markings. 



Figs. 37 to 41 

 37 



38 



39 and 40 

 41 



Figs. 42 and 43 HORMOTOMA GRACILIS var. GOODHUENSIS U. and S 1015 



Two specimens found in the Phylloporina bed of the Black River group near 

 Cannon Falls, Minnesota. 



Figs. 44 to 51 HORMOTOMA SALTERI Ulrich 1016 



44 to 47 A series of four specimens selected from several hundred to show variation in the 

 rim-like thickening of the upper edge of the whorls in the typical form of this 

 species. Fig. 44 is the most like the var. canadensis (Murchisonia [Hormotoma] 

 gracilis Salter, not Hall sp.) in which the rim is scarcely distinguishable. Upper 

 part of Trenton group, Mercer county, Kentucky. 



48 Two whorls of the original of flg. 47, x2, to show the surface markings, band and 



outline of whorls more distinctly. 



49 A small imperfect specimen, x2, of var. tennesseensis, from the Black River 



limestone of Tennessee. Has finer and more equal lines of growth than the 

 typical form of species. 



50 Doubtful specimen from the same formation and state as the preceding. The 



shell is too thick and the whorls relatively too high. 



51 A third fragment from this locality that is doubtful because the band is too 



wide. A fourth example from the same locality seems to be identical with the 

 var. canadensis. 



Figs. 52 to 55 SOLENOSPIRA PRISCA Billings sp 1022 



52 Silicifled specimen of var. extenuata. Lower division of the Stones River group 



at Murfreesboro, Tennessee. 



53 Diagrammatic figure made up from gutta percha impressions of several incom- 



plete moulds of the exterior collected at Beloit and Janesville, Wisconsin. 



54 Two whorls of the Tennessee form. x2. 



55 Three whorls of the northwestern form, x2, showing that they are relatively 



wider than in the Tennessee variety. 



Figs. 56 to 60 SOLENOSPJRA PAGODA Salter 1022 



56 and 57 Two views of a fragment, showing the form of the mouth, the four revolving 

 carioae and several of the fine lines of growth. The latter show that the outer 

 lip is notched and that the space between the central pair of ridges represents 

 a true slit-band. Phylloporina bed of the Black River group, near Cannon 

 Falls, Minnesota. 

 58 Same specimen in another view, x2, to show the form of the volutions more 



clearly and to admit of easier comparison with S. prisca. 



59 and 60 The apical portion, natural size, and two whorls x2, of a specimen from an equiv- 

 alent horizon at Porter's station in Wisconsin. Collection of Wisconsin 

 State University. 



Figs. 61 to 63 CtELOCAULUS CEHLERTI Ulrich 1020 



Two casts of the interior and the base of one, showing the numerous depressed 

 whorls and the narrow umbilical perforation. Trenton group, Jo Daviess 

 county, Illinois. 



Figs. 64 and 65 OMOSPIRA LATICINCTA Ulrich 945 



64 A large testiterious example of this species, imperfect below and at the apex. 



Black River limestone, Tennessee. 



65 A slightly oblique view from above of a portion of the last whorl of same, x2, 



showing the course of the regular lines of growth. 



Figs. 66 and 67 OMOSPIRA ALEXANDRA Billings sp 946 



66 An imperfect sillcifled shell of this species, from the top of the Black River lime- 



stone of Mercer county, Kentucky. The whorls are more rounded than in the 

 preceding species. 



67 A cast of the interior from the same formation at Dixon, Illinois, doubtfully 



referred to this species. 



Figs. 68 and 69 EOTOMARIA ELEVATA Ulrich 1005 



Two views of the nearly entire type of this species. Trenton group, Hartsville, 

 Tennessee. 



