Contributions to Palaeontology. 



163 



Miniska river. It is chiefly associated with Ptychaspis (^Dikelo- 

 cepJialus') granulosus of Owex. 



This is unquestionably identical with the glabella figured by Dr. 

 Owex, Loc. cit., Tab. 1, f. 3 a & 12; and Tab. 1 A, f. 5. The 

 pygidium ( Tab. 1, f. 3 b ) likewise corresponds with that figured 

 Plate i, f. 46 ; the former being a somewhat larger individual. 



The glabella of the young of this species bears some resemblance 

 to the glabella of the more convex forms of Dihelocephalus pepinen- 

 sis; but the posterior furrow is more oblique, and the second fur- 

 row more conspicuous, while the contour in front is more curved. 

 It likewise resembles, in some of its phases, the D. spiniger ; but 

 the frontal limb of this is nearly straight, and the glabella is more 

 truncate, while the glabellar furrows very nearly correspond. The 

 form of the fixed cheek, however, distinguishes it at once from 

 either of these, as well as from others of that genus. In young 

 specimens, the glabella resembles very closely that of Ptychaspis 

 (Dikelocephalus~) granulosus of Owex ; but the second glabellar fur- 

 row in that species is continued across the glabella, and the poste- 

 rior lobes are marked by a small tubercle at their extremities, while 

 the front contour is distinctive. 



Although referred by Dr. Owex to the Genus Dikelocephalus, 

 this species differs in having the sides of the glabella not parallel 

 throughout, but more particularly in the form of the fixed cheeks, 

 in the movable cheeks, and in the character of the palpebral lobes. 



PTYCHASPIS GRANULOSA. 



PLATE I. FIGS. 33-40. 

 Dikelocephalus granulosus : Otvex, Loc. cit., page 675, Tab. 1, f. 7 (and 5?). 



Head broad, with a narrow frontal border and wide cheeks. 



Glabella narrow, prominent, semicylindrical, of nearly 

 equal width throughout, or sometimes a little wider in 

 front than in the middle ; marked by two strong trans- 

 verse furrows which reach entirely across : the posterior 

 one is a little oblique at the extremities, and straight in 

 the middle ; the second one is direct, or scarcely curving. 

 The posterior lobe is wider, slightly bent forward, and 

 subnodose at its extremities ; while the extremities of the 



