178 SIXTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



GENUS AGNOSTUS ( Brongniart ). 

 AGNOSTUS JOSEPHA ( n. s.). 



PLATE VI. FIGS. 54 & 55. 



^'Agnostus orion(?) Billings" : Shumard in Transeations Acad. St. Louis, Vol. ii, p. 105. 

 Not Battus [Agnostus] orion of Baerande, Notice preliminaire, p. 16, 18-46 = Diplorrhina 

 orion, Coeda, 1847. 



Head semi-elliptical, a little wider than long; the sides usually 

 curving, sometimes straight for a part of their length, margined 

 by a flattened or concave narrow limb ; rather abruptly convex 

 at the sides : the posterior margin, just within the angles, is 

 produced on each side into a short spine. 



Glabella prominent, narrow, extending about two-thirds the 

 length of the head, and crossed by a shallow furroAv near its 

 anterior end : the posterior lobe is marked by an oblique fur- 

 row on each side, and a small node on the summit at the an- 

 terior termination. The triangular space on each side, between 

 the transverse and oblique furrows, is likewise elevated into a 

 low node. The posterior central portion is gibbous, narrowed 

 at the base, with a small tubercle on each side. A narrow lon- 

 gitudinal furrow extends from the apex of the glabella to the 

 marginal limb. 



Pygidium of the same form as the head, or a little wider : axis 

 prominent, subquadrangular, wider than long, nearly one-third 

 the length of the pygidium, bearing a node or short spine on 

 its posterior extremity ; sides and body of the pygidium (out- 

 side of the axis) highly convex. 



In some of the specimens, the sides are a little more straight 

 and parallel than those given in the figures ; and in several spe- 

 cimens, a truncation or slight emargination has been observed in 

 the anterior border. 



Fig. 54. The head of this species, three times enlarged. 



Fig. 55. The pygidium of the same, enlarged in the same proportions as the preceding. 



This species is common in some layers of gray sandstone, associated with 

 Conocephalites loisconsensis and Ftychaspis granulosa, at Trempaleau. It 

 occurs also at the mouth of Black river, and elsewhere on the Mississippi 

 jihout Lake Pepin. 



