396 The Arnerican Geologist. June, i892 



length from the apex. The tubercle forms a longitudinal medium 

 lobe in the anterior | of the axis. The tubercle is at the anterior 

 margin, slightly elevated above the general convexit}" of the axis, it 

 is less elevated just over the anterior pair of furrows, but behind 

 this point it rises to twice the hight and terminates abruptly 

 at the posterior furrow. The anterior lobes of the axis are dis- 

 tinctly separated from the tubercle b}^ a narrow groove; the 

 second two are not. Surface apparently smooth, but with indi- 

 <3ations of small wrinkles which unite with each other, so as to 

 give a reticulated aspect, similar to that of A. reticulatus Ang. 

 The species differs from A. tardus Barr, in having a shorter axis 

 in the pygidium, and in having the node of uniform hight its 

 whole length. 



Agnostus fabius Billings, 1865. Plate ix, fig. 10. 

 Diagnosis. — Head semi-elliptical, uniformly and moderately 

 convex. Liml) very narrow. Grlabella scarcely elevated above the 

 general surface, not defined in front; obscurely so in the posterior 

 half by the dorsal furrows, which are parallel, and disappear 

 about the middle of the head. Basal lobes small, triangular. 

 Pygidium slightly more elongated than the head. Limb narrow, 

 flat. Axis about ^ the whole width; it has two pairs of transverse 

 furrows, the posterior reaching the median line, where there is a 

 small rounded tu})ercle, located slightly behind the mid-length of 

 the axis. The anterior furrows are half way between the tuber- 

 cle and the front margin, their inner extremities separated by 

 about one-third the width of the axis. 



