1859.] EGEETON OLD KED EISHES. 135 



" The small east, fig. 9, shows the deep hollow of the eye-orbit of 

 Coccosteus, as scooped out of the under side of plate d, fig. 6. The 

 specimen from which it is taken shows the whole inferior surface of 

 the occipital buckler and the hollows of both eyes. 



" The cast, fig. 3, that of a head in a beautiful state of keeping, 

 seems to illustrate the profile of the head seen in the cast, fig. 6. 



" I would fain have sent you a few illustrative casts more, — among 

 others, a cast of the paddle-shaped plates which lay under the eyes, 

 and described the nether half of the orbit ; but my little box refuses 

 to accommodate more. These plates, however, you will find figured 

 by Agassiz in his ' Old Red,' tab. 8, and in tab. 9. fig. 1. The 

 narrow neck-like stem, which I have compared to the claw of an 

 anchor, swept round the eye-orbit ; and the rounded sweep of the 

 paddle-blade or anchor-fluke fitted into the hollow on the outer 

 edge of plate/, which is so well marked in my casts, figs. 1 & 6." 



Letter dated December 23, 1848. 



" I cannot regard the species of Coccosteus to which the plates 

 of my cast in last parcel (fig. 5), or that of the unique specimen 

 fig. 6, belong, as Coccosteus decipiens. Both its dorsal plate, 1, and 

 its occipital plate, a, are longer in proportion to their breadth than 

 those of that species. Agassiz, however (in tab. 10. fig. 1), has 

 figured an individual of this species, from my collection, as Coccosteus 

 decipiens. Its proportions are rather those of Coccosteus cuspidatus, 

 though its dimensions are smaller. The very fine head from which 

 the cast No. 1 was taken belonged to an individual of larger size 

 and greater proportional breadth." 



Note. — I quite agree in the propriety of considering this a distinct 

 species. In addition to the characters alluded to above are the 

 following: — The central abdominal plate has the posterior angle 

 more obtuse than the anterior one; and the angular or dagger- 

 shaped bone in advance of it is considerably narrower than in any 

 other species. The tubercles are very numerous and uniform in 

 .size. I propose to signalize the species as Coccosteus Milled. — P. E. 



L, tter dated Ft hrn.ari/ '■>. I v l!». 



"I send you a east of a tolerably good specimen of two of the 

 lateral plates of Coccosteus — those overlain on their upper edge by 

 the dor>al buckler. They have been sufficiently displaced in the 

 original to show the squamose sutures, which were not shown in the 

 cast of my onique specimen. Tin- pin which attached the cuirass 

 to the head belonged, as shown by one of nay former casts, to the 

 interior surface of plate h : its miter surface exhibits ;i minute 

 groove instead." 



1 have a subsequent Letter, dated January 26, L860, describing 

 the b\ ru t ore of the j .- 1 \\ b of ( 'oooostt us ; but a-* this subject w as com- 

 municated in a paper to the Phyaica] Bocietj of Edinburgh, and is 



