SOME NEW DEVONIC FOSSILS 



163 



that they are seldom seen except on casts of the ventral surface 

 of the border and in such cases the outermost sometimes assume 

 the aspect of a pair of subsidiary spines. The snout is axial, has 

 a broad base, is contracted in diameter medially and at the distal 

 extremity carries a trident the central process being axial, the 

 other two diverging palmately and all considerably extended. There 

 seems to be some variation in the length of this process but ap- 

 parently it was from one third to one half as long as the cephalon 

 itself. The entire process is flat. In the trilobed species of the 



Dalmanites (Probolium) biardi 



New Scotland beds, D. t r i d e n s, there is likewise noticeable 

 variation in respect to the development of these processes as shown 

 by the figures given in Palaeontology of Nezv York, v. 3, 1859, 

 pi. 75, fig. 3-6 ; it sometimes has them so much reduced 

 that the extremity takes on a spatulate outline. The genal spines 

 are relatively broad and short. The surface of the cheek below 

 the visual area is deeply grooved, the facial suture on the cheeks 

 does not lie in a furrow and the surface below the eyes shows only 

 rather obscure traces of confluent papillae. The general surface 



