SOME NEW DEVOXIC FOSSILS 



171 



appear that some of the tubercles at the crest of the frontal lobe 

 are extended into thick spinules. Parts of a pygidium indicate 

 that this organ was flat and extended and the margin carried long 

 flat spines. 



Lower Devonic. Grande Greve, P. O. 



Ceratocephala robinia nov. 



This form is known from various parts and one nearly entire 

 specimen, which attains much larger proportions than C. tuber- 



Ceratocephala robinia 



culata (Helderbergian) and yet is allied to both that species 

 and the C. callicephala from the Onondaga limestone. 

 Placing these species in comparison we may find the distinctive 

 characters expressed as follows: 





C. tuberculata 



1 

 C. callicephala! C. robinia 



Size 



Small 



Medium Large 



Neck ring 



With short stout spine 



With small spine With longer, stout and 

 somewhat curved 

 spine 



Thoracic segments 



Finely tubercled 



Regularly and coarsely [Coarsely tubercled 

 tubercled 



Pygidium 

 1st spines 



Moderately long 



Slender and longer 

 than 2d pair 



Very short 



2d spines 



Much longer 



Shorter than 1st pair 



Longer than 1st pair 



3d spines 



Large, stout' and twice 

 the length of 2d pair 



Not conspicuously the 

 largest of the series 



Sharp and slender, 

 longest 



4th spines 



Very short 



Relatively long and 

 slender 



Sharp and slender, more 

 than £ the length of 

 3d pair 



Surface 



Strongly tubercled 



Tubercled 



No tubercles 



