168 



Contributions to 'Paleontology. 



ILL^NURUS QUADRATUS (n. s.). 

 PLATE II. FIGS. 52-57. 



Head broad, semielliptical. Glabella convex, a little 

 longer than wide, without visible occipital or dorsal 

 furrow ; a scarcely perceptible groove along the poste- 

 rior margin; the width a little greater behind than be- 

 fore ; sides concave ; palpebral lobes marginal, a little 

 behind the middle of the glabella. 

 Facial suture cutting the contour of the front a little 

 within, or nearly in, a vertical line drawn through the 

 eye, and making a very gentle concave curve to the 

 outer margin of the palpebral lobe. 

 Movable cheeks scarcely longer than wide, with a deep 

 sinus below the middle, marking the form of the eye : 

 posterior extremities rounded, and straight upon the 

 posterior margin. 

 The middle lobe of the thorax is wide and moderately 

 convex ; the lateral lobes narrow, little convex, and the 

 extremities slightly bent backwards, and posteriorly 

 acute. A narrow shallow furrow runs through the 

 middle of the length of the segment. 

 Pygidium short, convex in front and marked near its mar- 

 gin by a narrow groove, rounded behind. 

 The specimens observed are the casts of dismembered portions 

 of the body; and occuring in sandstone, it is difficult to determine 

 all the characters. The glabella, pygidia and cheeks are preserved 

 in considerable numbers in a fragment of sandstone from near 

 Osceola mills on the St. Croix river, from a position near the middle 

 of the formation. 



In more extensive collections made at other localities, no frasr- 

 ment of this species has been observed ; and it is, therefore, with 

 probability, inferred that its horizontal range is restricted. 



