386 The American Geologist. . June, i892 



lar except the tubercle. The pygidium is semi-elliptical, some- 

 what wider than long, strongly elevated along the axis, trun- 

 cated in front at the lateral thirds. The axis is cylindro-conical, 

 width ^ the pygidium, length f; it bears an elongated tubercle 

 on the axial line at the anterior \ ; short furrows indent the sides 

 of the axis, opposite the ends of this tubercle. The side lobes 

 are narrow and divided at the extremity of the axis by a furrow, 

 connecting the dorsal and marginal furrows. 

 Lomlity. St. John group, at Porter's brook, St. Martin's. 



\gnostus acadicus Hartt, 1878. Plate ix, fig. 7. Syn. Aguostus 

 similis Hartt. 



Diagnosis. — Head convex, depressed. Limb narrow, slightly 

 elevated. Glabella slightly less than f of the length of the liead^ 

 long, elliptical, depressed convex, but more elevated than the 

 other parts of the head ; frontal lobe of the glabella, sub-circular 

 and occupying about ^ of the glabella; basal lobes small, but 

 distinct. Cheeks of the same width throughout and united in 

 front of the glabella; they are convex, more elevated along their 

 inner margins, but sloping outwards roundly and evenly. The 

 genial zone has a narrow, shallow, flat space or groove which fol- 

 lows the limb; on going posteriorly along the lateral margins it 

 loses gradually its width towards the posterior angles of the head. 

 Thorax unknown. 



Pygidium similar to the head. The limb slightly raised, separ- 

 ated from the sides by a shallow but well marked groove running 

 parallel to the margin. This groove widens at the point where it 

 bends to go forward along the sides, in such a way as to en- 

 croach on the thin out of the limb; just before reaching the an- 

 terior margin it narrows itself from the inner side, so as to cause 

 the side lobes to widen somewhat anteriorly. These are narrow, 

 flattened, about ^ as wide as the axis, narrowing to a point just 

 behind the axis where they do not unite. The axis 

 is about five-sixths of the length of the p3'gidium, lan- 

 ceolated, flattened, more elevated than the side lobes of the P3'gi- 

 dium. Dorsal furrows distinct. The axis has a small tubercle 

 located on the median line about ^ its length from the front mar- 

 gin. Surface smooth. 



Locality. St. John group, Saiat John, N. B. 



The head of this species approaches that of A.neon, Hall & Whitfield. 



