GASTROPODA— P LEV ROTO MARUDM. 



63 



XXX. Ormospira Uirich. 



High-spired, of many rapidly enlarging volutions. Structure 

 as in Rhaphistoma, but with very loosely embracing whorls. 

 Ordovicic. 

 89. 0. laticincta Uirich. (Fig. 854, b, c.) Ordovicic. 



Large ; angle between shoulder and body of whorl obtuse ; 



FlG. 854. a, Scalites angulahis ; b, c, Ormospira laticincta, with enlargement of slit 

 band ; d, Ormospira alexandra. (After Uirich, Pal. Minn.) 



shoulder flat; striae interrupted near middle by revolving spiral, at 

 which they change from convex to concave. 



Black River of Tennessee. 

 90. 0. alexandra Bill. (Fig. 854, d.) Ordovicic. 



With smaller apical angle and more rounded whorls than pre- 

 ceding. 



Black River of Canada and Kentucky. 



XXXI. Lophospira Whitfield. 

 Shells with more or less elevated spires ; close coiled whorls 

 except in senescent (phylogerontic) species. Whorls angular, gen- 

 erally with several carinae of which the central one forms a strong 

 keel and is marked by an obtusely rounded peripheral "band" 

 which is often marked with spirals of which the central one is 

 heaviest. Umbilicus nearly always present. Outer lip notched 

 but without slit. Ordovicic-Devonic. 



A. Lines of growth forming very slight or no peripheral reentrant. 



