riilyctcTiiaspis, a New Genus of Coccosteidre. 233 



angles being confluent into one of considerably greater pro- 

 minence. In front we liave tlie same more anterior direction 

 of the orbital excavations, bounded by tlie post-orbital and 

 ante-orbital prominences, and between the latter (of each 

 side) we have a similar gentle concavity for the rostral or 

 ethmoidal plate. 



It is the internal or concave aspect of the shield which is 

 here exhibited, and it is extremely difficult to recognise any 

 sutures except tliat separating off tlie median occipital, whicli 

 shows distinctly enough that tliis plate had the same 

 elongated pointed form as in the Canadian species. The 

 bone being considerably splintered away, especially on tlie 

 rioht side, some of the external markings are seen in 

 impression, showing that the surface was sculptured with 

 tubercles of a comparatively large size. The course of the 

 lateral-line groove may be distinctly enough seen, its dis- 

 position being quite similar to that in P. Acaclicus, — the 

 main groove, starting in the external occipital, passing 

 obliquely forwards and inwards to the ossific centre of the 

 plate, then proceeding forwards and slightly outwards for 

 a little distance, and sending a branch obliquely backwards 

 and outwards to the external angle of the shield, after which 

 it proceeds forwards and slightly inwards to behind the 

 postero-orbital angle. There, a ridge on the inner surface 

 of the shield indicates that it turns at an acute ansfle 



o 



backwards and inw^ards to the middle of the central 

 plate in a manner quite similar to that already seen in 

 P. Acadicus. 



Figure 4 is a diagram-sketch of the plaster cast sent me by 

 Mr Smith Woodward, taken from a specimen which clearly 

 belongs to the same species, and which shows many points 

 with o-reater clearness than that belonoincj to the Edinbur2:h 

 Museum, the outer surface being here displayed. It 

 measures tw^o inches in length by tw^o in breadth, but has 

 a piece broken off at the posterior part of the left side, while 

 on the right it looks as if the prominent external angle were 

 covered by the matrix. The surface is covered by a coarse 

 pustular tuberculation, omitted in the figure, showing at 

 places a little, but not much, of the concentric arrangement ; 



