368 Review of the Neio York Geological Reports. 



Casts of a Pleurotomaria rather more slender and elongated 

 than figure 1, occur in the lead-bearing rock of Iowa. The Del- 

 thyris expansus, (fig. 2,) appears identical with a species found at 

 Eagle Point, Iowa. 



The foregoing figures of the Trenton limestone, have been 

 selected from their close analogy to western species. 



Of the remaining fossils of this formation we can only give a list. 



Isotelus planus, Bumastis Trenionensis, (fig. 1, p. 364,) Ca- 

 lymene ; Illcenus Trentonensis, (fig. 3, p. 364,) Trocholites 



