650 



NORTH AMERICAN INDEX FOSSILS. 



Tennessee (var. tennesseensis) ; Trenton of Kentucky (also var. 



nitida). 



146. H. bellicincta (Hall). (Fig. 887, a.) Ordovicic. 



Stout, with rapidly enlarging whorls, whose 

 diameter is about twice their height ; apical 

 angle 42 to 50 ; small umbilicus and flat 

 band. 



In the Trenton limestone of New York and 

 Canada ; also in Minnesota, etc. A great 

 number of forms have generally been identified 

 with this species, the Murchisonia bellicincta of 

 Hall. 

 147. H. trentonensis U. and S. (Figs. 2>^>y y 



b\ 888.) Ordovicic. 



Longer and more slender than preceding, 

 apical angle averaging 35 . Commonly con- 

 founded with H. bellicincta Hall. 



Occur generally as internal moulds in the 

 Trenton limestone of New York and Canada. 

 Pal - Also in Minnesota and Illinois, Kentucky, 

 and Tennessee, though rarely. 



148. H. major (Hall). (Fig, 889.) Ordovicic. 

 Large, apical angle about 25 ° ; generally preserved as internal 



molds. In these the suture is deep, with an angulation on the 

 upper side of the whorl and a flat space beyond this. In the shell 

 the whorls embrace far up on the preceding one. 



Trenton (Galena) of Minnesota, Wisconsin, Iowa, Missouri, 

 Dakota. 



149. H. subcarinata Grabau. Siluric. 

 Differs from H. salteri in its looser coiling, the exposed body of 



whorl being often half again as wide as the shoulder and bearing 

 a faint indication of a lower spiral. 



In the upper Monroe of Michigan, Ohio, and Ontario. 



150. H. desiderata Hall. (Fig. 890.) Devonic. 

 Large, slender, embracing to within one half or two thirds the 



shoulder width ; shoulder flat above, gently convex near band, 

 which is flattened or slightly concave. 



Onondaga of Falls of Ohio and New York (?). 



Fig. 888. Hormoto- 

 ma trentonensis. ( After 

 Ulrich and Scof. 

 Minn.) 



