CRUSTACEA. 213 



rical, the outer portion of the posterior slope being a little more convex than 

 the inner. 



In the third plate the form is much as in the preceding, but is broader, 

 the apex more central and not so strongly incurved, the antero-lateral slopes 

 more conspicuous and the posterior -lope narrow and unsymmetrical. 



The fourth plate is almost the reverse of the first in form; the posterior 

 area is abbreviated, very narrow and slightly concave just beneath the 

 elevated apex; the outer lateral slope is broad and flat. Whether the 

 plate bears a median carina and differs as widely in the size of its lateral 

 laces as in the first plate, cannot be determined, as it is largely covered by 

 the preceding plate of the range. 



The fifth plate is broken and its form cannot be satisfactorily determined. 



In the right vertical range the plates were evidently symmetrical with those 

 of the left, but have been somewhat displaced from their normal position. 

 The first is in place: the second has been pushed out of its place and is not 

 apparent, unless it is represented by the upturned lower surface of a plate 

 visible near the lower portion of the specimen lying beneath the other plates ; 

 the third plate is pushed backward so as to show the strongly carinate anterior 

 surface of the fourth plate projecting beyond its anterior edge ; beneath this 

 lies also the anterior edge of the fifth plate, showing that it also is carinate ; 

 and back of them all lies the sixth plate with a posterior apex, truncate 

 behind, lateral slopes broad, the outer being the broader, and separated from 

 the inner by a carina. Although this plate does not appear in the left range 

 it may be represented by a fragment lying beneath the inner edge of the 

 fourth plate of that range. 



The axial range is composed of small plates having about one-third the 

 diameter of those of the lateral ranges. These differ considerably in form, 

 but appear to be bi-symmetrical. Three are to be seen in juxtaposition on 

 the anterior portion of the specimen, and a fourth is displaced and lies be- 

 hind the inner posterior edge of the fourth plate of left range. 



In addition to these three ranges of plates is a vertical row of spines, 

 which, whatever their normal position, lie in a more or less detached condi- 



