Genus Agnostus. — Vogdes. . 389 



increases in width going backwards as far as the posterior lateral 

 angles, where it is as wide as the lateral lobe of the p3'gidium, 

 but harrows again towards the extremity of the pygidiuni. The 

 limb increases in width from the front as far as the lateral spines, 

 behind which it is constricted; at the anterior end it is angulated 

 towards the axis, in the rear third broadlj^ rounded. 



Locality. 8t. John group, Portland and at Hanford brook, St. Mar- 

 tin's. 



The species differs but slightly from Agnostus fallax YSiT.ferox Tullb. 

 from the Scandinavian formation at Andrarum with Paradoxides tessini. 



Agnostus vir var. concmnus Matthew, 1885. Plate ix, fig. 13. 

 This variety varies but slightly from Agnostus vir. 



DIKELOCEPHALUS ZONE. 

 Section LONGIFRONTES. 



Agnostus americanus Billings, 1860. 

 Syn. Agnostus richmondensis Walcott. Plate ix, figs. 5 and 11. 

 Diagnosis. — Head oblong, semi-oval, rather strongl}" convex, 

 most elevated at the posterior quarter of the length, thence de- 

 scending with a depressed convex slope in all directions to the 

 sides and front. Limb verj^ narrow. The glabella is elongate 

 oval, width ^ that of the tvhole head, length rather- more than f 

 the length of the head. It has two transverse furrows which 

 completely or partially divide it into three lobes. The anterior fur- 

 row extends all across at ^ or a little more of the length from the 

 front. The posterior furrow is interrupted in the middle, and is 

 only distinctly seen on each side, penetrating ^ the width, while 

 its position is a little in advance of the posterior third of the 

 length of the glabella. The space between the two inner extrem- 

 ities of the posterior furrows is occupied by a low conical tuber- 

 cle, with the apex directed backwards. Basal lobes small and 

 triangular. Dorsal groove distinct. Cheeks divided in front of 

 the glabella by a furrow. The surface is ornamented by from 15 

 to 20 irregular, slightly impressed radiating rugose stride. The 

 pygidium is striated like the head. The axis has three lobes with 

 an elongated median tubercle, extending across the anterior and 

 middle lobes ; the posterior lobe is equal in size to the other lobes. 



Locality. Point Levis, Quebec. 



This species approaches A. trisectus Salter, which occurs at Andrarum, 

 Sweden with the genus Peltura. 



