CONTRIBUTIONS TO PALiEONTOLOGY. 173 



PTYCHASPIS GRANULOSA. 



PLATE VI. FIGS. 33-40. M'"^'/^^ 

 Dikeloccphalus granulosus : Owen, Loc. cit., page 575, Tab. I, 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 transverse furrows which 

 reach entirely across : the posterior one is a little oblique at 

 the extremities, and straight in the middle j the second one is 

 direct, or scarcely curving. The posterior lobe is wider, slightly 

 bent forward, and subnodose at its extremities ; while the ex- 

 tremities of the second annulation are slightly curved forward, 

 but not expanded. At the extremities of the posterior annula- 

 tion, and separated from it by an indentation, there is on each 

 side a small node lying nearly in the line of the dorsal furrow. 



Occipital furrow strongly marked, straight in the middle, slightly 

 curving forward at the extremities, and continued in the fixed 

 cheeks : occipital ring narrow, prominent, and rising above 

 the convexity of the glabella. Dorsal furrow strongly defined, 

 slightly interrupted behind by the little nodes before men- 

 tioned. The frontal limb is depressed, a little convex in front 

 of the furrow, and bent abruptly downwards. 



The fixed cheeks rise abruptly from the frontal limb, to a promi- 

 nence continued from the palpebral lobe to the dorsal furrow; 

 the principal part of the area from the eye backwards being 

 depressed convex, and produced into an angular termination at 

 the extremity of the posterior limb. Surface strongly striate. 



The surface cliaracters are rarely seen in the casts ; but in the impres- 

 sions in the sandstone, they may he detected. The peculiar form of the 

 glabella and fixed cheeks, the anterior position of the e3^es, and strongly 

 furrowed glabella with prominent rounded anterior lobe, are characters 

 which readily distinguish this species from any other, except the young of 

 Ftychaspis ( D.) miniscaensis. ■ 



Dr. Owen has given the following 



*' Specific character. This species is distinguished particularly by 

 " the glabella and cheek-plates, as far as they are preserved, 

 " being studded with minute granules. The glabella is divided 

 " by three furrows into four segments : the posterior segment 

 *' terminates on either side in two obscure basal tubercles. '^ 



