10 
TOPULAR SCIENCE REVIEW. 
more numerous as they reach the dorsal fin, and recede thence to 
the slender extremity of the body. 
“ In but few of the specimens,” writes Professor Huxley,* 
“ which I have had the opportunity of observing, has the ex- 
ternal surface of the cephalic shield been well exhibited, or 
preserved over any considerable surface. 
Where best shown it is somewhat un- 
even, and presents that curious appa- 
rent division into polygonal (usually 
hexagonal) arese which has been de- 
scribed by Professor Agassiz (Woodcut, 
Fig. 6). On examining the apparent 
sutures closely, however, they have not 
presented to my observation precisely 
the appearance figured by him. They 
appear rather as if short, delicate, red- 
dish brown lines had been ruled across 
the line of junction of the sides of the 
hexagons, for some way towards the 
centre of each hexagon ; and these lines 
are so gently convergent as to seem nearly parallel. Neither 
do I remember to have met with such strongly marked central 
elevations as those represented in the figure cited.” 
Having carefully examinee! numerous recent specimens of 
Fig. 6. 
POLYGONAL ORNAMENT FROM 
head-shield of Hemicy- 
claspis Murckisoni (after 
Lankester) ; magnified 7 
diameters. 
Fig. 7. 
Fig. 7 a. 
Fig. 7.— outline of head shield of Eucephalaspis Pagei (Lankr.). 
7 a . — ornament of the same, magnified 7 diameters (after Lankester). 
armour-plated fishes, I was much struck by the foregoing 
observation of Professor Huxley; as not only applicable to 
Cephalaspis , but to the dermal armour of the entire body of 
* Op. cit. p. 279, 
