Identity of Atops trilineatus with Triarthrus Beckii. 325 
tax and abdomen are varying with the distance from the buckler. 
The outer crust of this specimen is removed and the small spines 
on the back are nearly obliterated. 
‘Fig . 2b is a specimen preserving the maxillary alse of the 
buckier, which are partially displaced and compressed. Buckl 
y twice as wide as long. 
Fig. 2c is a fragment of the thorax and caudal extremity very 
perfectly preserved, and presenting the usual proportions of this 
part of the animal when not distorted. 
Figs. 2d, 2e, are two specimens of the buckler, the one preserv- 
ing the maxillar ary — while they are wanting in the other. 
The proportions of length and breadth are slightly different, but 
neither of them twice as wide as long. 
Fig. 22 is the imperfect buck- 
ler of a specimen more than usu- 
ally convex in the middle and 
having the lobes more distinetly 
Marked. Fig, 2/f is a buckler hav- 
ing a width scarcely once. and a 
half the length. This is an example of the specimens described 
by Prof. Eaton and Prof. Green.* It is very convex and appar- 
ently contracted or bent downwards at a a other more 
Convex specimens are of common occurre he proportions 
between the lateral and middle lobes of a ‘buckler, it will be 
Reema ee ee 
"See Eaton's Geological Text-book, vol. i, fig. 2, and Green’s Monograph 
Plate, fig. 6. 
