288 TJic American Geologist. May, isos 
In all of the forms here referred to Agranliis the eyes are far re- 
moved from the glabella, and the facial suture extends from the eye 
with a slight curve directly to the lateral margin cutting it at nearly 
a right angle, and posteriorly it cuts the margin just within the genal 
angle. The glabella is clearly defined but shows marked differences 
in the several groups of specimens. 
Agraulus convexus Whitfield. 
Arionellus [Agraulos] convexus Whitfield. Ann. Rept. Wis. Geol. 
Survey for 1877, p. 57, 1878. 
ArioncUux coni'cxtis Whitfield, (xeol. of Wisconsin, \ol. \W p. igo, 
1882. 
Plate XX, FisR. 9, 10 and il. Plato XXI, Fiffi^. 3 and 7. 
Cephalic shield strongly convex; glabella strongly defined by the 
dorsal furrows, somewhat narrower at anterior extremity and bound- 
ed by almost a straight line which curves narrowly to the dorsal fur- 
rows; three faint oblique lateral furrows on the glabella; occipital fur- 
row deep above but disappearing at the dorsal furrows and again ' 
continued faintly across the posterior portion of the fixed cheek; fixed 
cheeks a little more than half as wide as the glabella, strongly arched 
at the eyes: frontal limb deeply cut by a median groove which marks 
off an anterior marginal rim, wider and more prominent in front 
than at the lateral margins, forming a rounded and thickened projec- 
tion extending at a considerable angle beyond the general convex 
contour of the shield. Facial suture runs from the eyes anteriorly out- 
ward so as to cut the lateral margin at almost a right angle and pos- 
teriorly runs abruptly to the margin within the genal angle; eyes pos- 
terior to middle of glabella; length of glabella 7 mm. without ring; 
length of shield 12 mm.; width of glabella anterior 4^-2 mm.; poster- 
ior 6 mm.; width of cheek 3 mm.; frontal limb zVa rom- The pygid- 
ium, fig. II. is supposed to belong to this species. 
Formation and locality: Upper Dresbach, Taylor's Falls. 
In addition to the form for which the above description was writ- 
ten there are two others which are so similar in most points except 
size that they are provisionally regarded as stages in the growth of 
this species. One (A) is larger and the other (B) smaller than the 
measurements given. The former is probably a senile individual and 
the latter an immature form. 
Variety A. 
Plato XX, Figs. 1 and 2. Plate XXI, Fig. .5. 
Cephalic shield more flattened giving a broader aspect to the 
head. Markedly less convex over the eyes. Occipital furrow imper- 
fectly marked; glabella smooth; median groove very faintly traced 
and the marginal rim follows the general convex contour of the rest 
of the shield. 
Variety B. 
Plato XX, Figs. 5 and 6. 
Form rather small. The cephalic shield is semicircular to lunate, 
strongly convex, greater width than length; glabella anteriorly con- 
