Contributions to Palaeontology. 



121 



DIKELOCEPHALUS MINNESOTENSIS, var. LIMB AT US. 

 PLATE IV. FIG. 12. 



A single fragment shows the anterior part of the gla- 

 bella, and nearly the whole of the frontal limb. In this 

 specimen the anterolateral angle of the frontal limb is 

 more rounded, and the anterior margin elevated in a 

 distinct border which does not appear to be thickened. 

 "Within this border are a few wrinkled striae, directed 

 towards the glabella. In a single small individual from 

 Lagrange mountain, I have seen a similar but less defined 

 border. 



Without other specimens, I ain unwilling to indicate this as a 

 distinct species. It occurs with D. minnesotensis and D. pepinensis, 

 at Lagrange mountain. 



DIKELOCEPHALUS MINNESOTENSIS, var. 

 PLATE IV, FIG. 11; AND PLATE V, FIG. 9. 



General form of head and glabella as in D. minnesotensis. 

 Glabella moderately convex, and slightly narrowing in 

 front of the eyes. Occipital furrow straight : posterior 

 glabellar furrows oblique ; the anterior one slightly 

 marked, and nearly straight. The frontal limb is 

 rounded at the antero-lateral angles, and slightly ex- 

 tended in the middle. 



The marked difference between this form and the D. minnesoten- 

 sis is in the frontal limb, which is extended in the middle so as to 

 interrupt the continuous curve of the contour. A single individual, 

 having this feature of the frontal limb in a marked degree, was 

 found at Lagrange mountain ; while two other individuals have 

 been found at Stillwater, in the Lower Magnesian limestone or 

 Calciferous sandstone. 



These differences, of apparently minor importance, might not 

 be regarded as worthy of specific distinction ; but we have, at the 



[Trans. v.~\ 16 



