184 Cincinnati Soctety of Natural History.- 
pointing mainly upwards and a little forward; it arises from the 
dorsal slope a little behind the center of the length of valve. 
This species is associated with 4. spinosa, Hall sp., but is 
generally larger, and less symmetrical, while the two marginal 
lobes impart an abnormal appearance to the valves that is quite 
foreign to that species. 
Position and locality : Shales of the Niagara group, at Leckport, 
NG: } 
ZECHMINA MARGINATA, N. Sp. 
Plate XVI, Fig. 5. 
Size: Length, 0.6 mm.; height, o.41 mm_-; Jenethenspme, 
0.75 mm. 
Valves small, elongate, narrowest anteriorly, with the dorsal 
edge straight and long, the angles obtuse, and the free margins 
forming nearly a semicircle. A_ slightly elevated marginal rim. 
Spine very long and slender. The marginal rim allies the species 
to 4. spinosa, but the valves are more elongate and the spine 
much longer. In both of these features the species approaches the 
Wenlock 4. cuspidata, Jones, but that form is without a marginal 
rim, and has the base of the spine stronger. 
Formation and locality: Shales of the Hamilton group, 18-mile 
creek, N. Y. : 
HALEIEDLAS) Cena 
Valves similar to Primitza, but with a larger sulcus, narrow at the 
dorsal edge, and widening as it extends downward. Posterior 
lobe smaller than the anterior; the latter generally divided at 
or near the straight dorsal edge. Surface of lobes coarsely sculp- 
tured, or reticulate, perhaps also smooth, ventral edge thick, 
generally with a ‘‘ frill” ora rim-like projection over the contact 
edges of the valves. 
In the present state of our knowledge it is exceedingly difficult 
to draw up a satisfactory description of this genus. I am con- 
vinced, however, that the species for whose reception this new 
genus is proposed are not /vzmtta any more than are those for 

*Named after Dr. James Hall, of Albany, N. Y. He requires no intro- 
duction. 
