GASTROPODA— MURCHISONIDJE. 



649 



144. H. gracilis (Hall). (Figs. 885, a-d; 886, a-d.) Ordovicic. 



Slender, small, and rather loosely coiled, the whorls embracing 

 very little, generally rounded or slightly angulated. 



A number of varieties have been recognized, one or another of 

 which occurs in most of the Trenton and Lorraine localities in 



c d 



FlG. 885. a, Hormotoma gracilis, 

 typical form ; b, var. sublaxa ; c. 

 var. multivolvis ; d, var. angusta. 



Fig. 886. a, Hormotoma graci- 

 lis, part of fig. a enlarged ; b> var. 

 sublaxa, part of b enlarged, X 2 * 



c, another specimen of same, X 2 5 



d, var. angusta, X 2 - 



eastern United States and Canada. It ranges as far down as the 

 Stones River group, and into the Chazy of Lake Champlain. 

 145. H. salteri Ulrich. (Fig. 887, c, d.) Ordovicic. 



Fig. 887. a, Hormotoma bellicincta; b, H. trentonensis ; c, d, H. salteri. 

 (After Ulrich, Pal. Minn.) 



Large, and with greater apical angle than H. gracilis ; whorls 

 embracing to two thirds or less shoulder width ; faint subsutural 

 band present. 



Black River of Paquettes Rapids, Canada (var. canadensis) and 



