592 



DR RAMSAY H. TRAQUAIR ON A NEW SPECIES OF CEPHALASPIS 



Herefordshire. Here, however, the cornua may be said to be obsolete (or undeveloped), 

 while these projections in the Argyllshire species, though short, are yet quite distinct. 



Description. — Fig. 1 in Plate represents a head nearly perfect in its contour, and 

 more than usually uncompressed. It measures If inch in length, by about the same in 

 greatest breadth, allowing for a slight deficiency of the cornual region of the right side. 

 The upper-aspect of the shield shows a flat margin, about £ inch in breadth, extending 



/j.f. 



Fig, 2. — Of C. Lornensis, Traq. 



Fig. 3. — Of C. Murchisoni, Eg. 



Fig. 1. — Outline of the cranial 

 shield of Cephalaspis LyclH, Ag. 



or., orbit ; p.o.v., post-orbital valley ; c, cornu ; p.s., posterior spine ; p.m., posterior margin ; p. a., posterior angle. 



from cornu to cornu round the front, within which the surface is convexly arched. 

 Anteriorly the contour of the head is bluntly rounded ; posteriorly the left cornu, which 

 is completely shown, is short and bluntly pointed, and does not extend as far back as 

 the posterior median point of the shield, nor even as far back as the posterior lateral 

 angle.* The eyes are placed considerably in front of the middle of the shield, for the 

 distance from the prominence of the posterior margin to a point midway between the 

 orbits exceeds that from the same point to the front by y g of an inch, or about one-sixth 

 part of the entire length of the head. Each of the oval orbits measures -^ inch in 

 length, and the two are rather less than the same distance apart. The antorbitaJ 

 prominences and valley are well marked, as is likewise the post-orbital valley, the latter 

 being succeeded by a ridge ending in the posterior spine, which is, however, not 

 prominent, and forms rather an obtusely angular point. 



The substance of the test is present pretty nearly all over, and in front of the orbits 

 indications of the external ornament are seen, apparently consisting of a very minute 

 granulation. 



Fig. 2 in Plate represents another nearly perfect cephalic shield, which is, however, 

 compressed into a condition of nearly absolute flatness. In size, in proportion, aud in 

 eontour, it closely agrees with the one just described. But the greater part of the bony 

 substance being removed, the impressions of the radiating blood-vessels of the lower 

 aspect are very distinctly exhibited. 



* Id pome specimens the cornu extends back as Ear as the posterior lateral angle, but in none does it go as far 

 posterior median point of the shield. 



