Br. R. H. Traquair — A Neic Genus of Coccosteidce. 59 



ever, a short time after communicating with Mr. Smith Wood- 

 ward on the subject, I received a letter from that gentleman 

 informing me that he had since discovered, in the stores of the British 

 Museum, quite a number of specimens apparently identical with 

 that to which I had referred. He also kindly forwarded to me a 

 plaster cast of one of them, as well as outlines in pencil of two 

 others. 



In PI. III. Fig. 3, I have given a sketch of the specimen in the 

 Edinburgh Museum. It measures If inches in length, and in general 

 form resembles the cranial shield of P. Acadicus, except that at the 

 back it is more produced outwards, as in Coccosteus, the postero- and 

 antero-external angles being confluent into one of considerably greater 

 prominence. In front we have the same more anterior direction of 

 the^orbital excavations, bounded by the 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 recognize any sutures 

 except that separating off the median occipital, which shows distinctly 

 enough that this plate had the same elongated pointed form as in 

 the Canadian species. The bone being considerably splintered away, 

 especially on the right 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 disposition being quite similar 

 to that in P. Acadicus, — the main groove, starting in the external 

 occipital, passing obliquely forwards and inwards to the ossiBc centre 

 of the plate, then proceeding forwards and slightly outwards for a 

 little distance, and sending a branch obliquely backwards and out- 

 wards 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 angle backwards and inwards 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 

 greater clearness than that belonging to the Edinburgh Museum, 

 the outer surface being here displayed. It measures two inches in 

 length by two 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 ; 

 the course of the lateral-line grooves is clearly discernible, while 

 the form and arrangement of the constituent bones may be 

 pretty fairly made out, both by actual indications of sutures 

 as well as by radiating lines where the surface has been abraded. 

 It is clear also, from both specimens, that these bones were quite 



