666 THE PALEONTOLOGY OF MINNESOTA. 
(Dicranella marginata. 
DIcRANELLA MARGINATA, 2. Sp. 
~ PLATE XLIV, FIGS. 27—28. 
Sizk.—Length 1.7 mm.; hight 1.22 mm ; thickness 1.0 mm. 
In this species the valves are much higher, especially in the posterior part, than 
in the two preceding species, the border, though wanting anteriorly, is much thicker 
and projects outward as much as downward or forward, while, instead of horn-like 
processes, we have two very unequal lobes, the posterior of which is comparatively 
very small, failing to reach the dorsal edge by a distance almost equalling its length, 
the anterior one (centrally situated) large, swollen in the middle, high and obtusely 
pointed above, the extremity reaching the dorsal edge or projecting slightly beyond 
it. The whole carapace also is thicker and has a more robust appearance. The 
peculiarities are strongly marked and conspicuous, and it does not seem likely that 
collectors will experience any trouble in recognizing the species. 
Formation and locality—Lower part of the Trenton shales (Rhinidictya bed), near Fountain, 
Minnesota. 
DICRANELLA ? SIMPLEX, ”. Sp. 
PLATE XLIV, FIGS. 4—25. PLATE XLVI, FIG. 42. 
_Size.— Length 0.98 mm.; hight 0.67 mm.; thickness 0.35 mm. 
Valves moderately convex, subelliptical; dorsal angles rounded, hinge line rather 
short; ends equal, rounded; ventral margin ‘rather strongly convex; edges simple, 
without border. A strongly elevated, oblique, conical prominence just within and 
behind the center of the dorsal edge; another large tubercle, in this case rounded 
instead of conical and ovate in outline, near the center of the posterior half and like 
the other reaching the dorsal edge; between the two a rather deep sulcus. A third 
tubercle, of irregular form and nearly as large as the second, occurs just within the 
upper half of the posterior edge. 
This species is evidently related to the Cincinnati form first called Leperditia 
byrnesi by Mr. Miller, and recently referred to Zichmina by Prof. Jones. That species 
however has only one posterior tubercle and a central oblique spine, while D. ? sim- 
plex has all three. The outline of the latter also is more convex ventrally. Of 
Minnesota Ostracoda, there is none sufficiently like it to require comparisons. 
Formation and locality.—Lower part of the Trenton shales (Rhinidictya bed), near Fountain, Minn. 
