102 TRANS. OF THE ACAD. OF SCIENCE. 



clinling the neck segment equal to the width at the base, 

 sides gently convex, neck furrow straight, moderately deep 

 and well defined; neck segment short, semielliptical, with the 

 sides gently rounded ; dorsal furrows distinct all around, as 

 deeply impressed as the neck furrow, and marked opposite 

 each angle of the glabella in front with a minute circular de- 

 pression ; no lateral furrows visible on any of the specimens 

 under examination ; front margin rounded and occupying 

 about one fourth the total length of the head; movable 

 cheeks regularly convex, margined with a narrow, rounded, 

 raised border, genal angles prolonged into long, slender, 

 curved spines. 



Length of head, 0.22 of an inch : length of glabella, 0.16; 

 greatest width, 0.11. 



The general contour of the head of this species when de- 

 prived of the movable cheeks reminds one of the head of 

 Ho molonatus delphinocephalus. 



Geol. Pos. & Loc. — The glabella and cheeks occur in great 

 profusion in soft ferruginous sandstone, of the age of the 

 Potsdam Sandstone, near the mouth of Lawrence creek, a 

 small tributary of St. Croix river, Minnesota. I have not ob- 

 served it at any other locality in the Northwest. 



CONOCEPIIALITES IoWENSIS, Owen Sp. 



Dikelocephalus (?) Iowensis, Owen. Geol. Rep. Iowa, Wisconsin and Slinnesota, Tab. 1, 



fig. 4, and Tab. 1 A, fig. 13. 

 Crepicephalus, id. ibid, Tab. 1 A, fig. 10, 16 & 18. 

 Undet. Trilobite, id. ibid, Tab. 1 A, fig. ii. 

 Lonchocephalus, id. ibid, Tab. 1 A, fig. 15. 



Head moderately large, flattened convex ; glabella gently 

 convex, truncated conical, length excluding neck segment 

 equal to the width at base, front gently rounded, no traces of 

 lateral furrows; neck furrow linear, sharply impressed and 

 somewhat shallower in the middle than at the extremities ; 

 neck segment not elevated above the curve of the glabella, 

 with sides converging rapidly from the neck furrow to the 

 posterior margin, which latter is short and straight; dorsal fur- 

 rows narrow and rather strongly impressed around the sides 

 and front of the glabella; front margin forming about one 

 fifth the total length of the head, having a deep transverse 

 groove situated in advance of the middle, and a cord-like ros- 

 trum in front ; immovable cheeks flattened convex, not as high 

 as the glabella, palpebral lobes separated from the cheeks by 

 a strong sigmoid furrow contracted at extremity in front. 



Thorax and movable cheeks unknown. 



Pygidium subquadrangular, sides converging from behind 

 forwards at an angle of 25°; margin wide, flattened, termin- 

 ating on each side posteriorly in two long, slender, slightly 



