CONTRIBUTIONS TO PALEONTOLOGY. 143 



by four distinct ribs which are deeply divided throughout their 

 leugthj and become merged in the flattened limb : the anterior 

 simple rib is prominent, subangular, and continued to the margin 

 of the border. The contour of the margin is apparently continu- 

 ous, and uninterrupted by spiniform extensions. 



This species is readily distinguished from the preceding, by the narrow 

 frontal limb of the glabella ; in the cheeks, by the long spine ; and in the 

 pygidium, by the more prominent axis and less expanded border, without 

 the posterior spiniform extensions. 



Plate ix, Fjg.1, shows the form of the glabella and fixed cheeks. 

 Fig. 2. The pygidium. 

 Fig. 3. A movable cheek. 

 Fig. 4. The hypostoma. 



In the collection from Lagrange mountain in Minnesota, this species 

 greatly outnumbers its associate the D. ininnesotenals. It is not known to 

 attain so large a size, nor does it occur in other localities so frequently, as 

 that species. In the Mazomania collections I have seen but a single indivi- 

 dual, and I have no specimens from any other place. Dr. Owen has cited 

 only the locality of Lagrange mountain for this species. 



DIKELOCEPHALUS SPINIGER ( n. s.). 



PLATE X. PIGS.l, 2 & 3? 



Glabella somewhat semicylindrical, very convex ; sides gently 

 converging, truncate in front; length little greater than the width : 

 posterior furrows very oblique and deeply impressed for nearly 

 one - third the width of the glabella, and continued by a more 

 shallow furrow across the summit; second furrows indented at 

 the sides, and continued across the glabella in a scarcely percep- 

 tible impression. The anterior furrows are slight indentations in 

 the sides of the glabella, leaving a very narrow anterior lobe. The 

 occipital furrow is deepl|^ impressed, straight in the middle, and 

 bending a little forward towards ths extremities : occipital ring 

 convex above, a little curving forward at the sides and very pro- 

 minent in the middle, supporting a spine. Dorsal furrows strongly 

 impressed, and more deeply marked in front of the glabella. The 

 frontal limb is a regularly convex elevated band. 



Fixed cheeks narrow at the sides, expanding in the direction of the 

 palpebral lobes, which are defined by a strong furrow. The po- 

 sterior limb is unknown. 



In the same fragment of rock with the glabella, there is a pygi- 

 dium which I have presumed to belong to this species. The axis 



