PLATE 62. 



Fig. 1,2. 43. 1. ISOTELTJS GIGAS. (Pao^. 231.) 



I a. A specimen folded so that the two extremities meet. The fossil is rarely found in this condition ; and in 

 many instances where it has originally assumed this form, it has been subsequently crushed. 



1 b. The caudal shield of a young individual, showing the marks of the articulations, and preserving the tri- 

 lobate form more perfectly than older specimens. 



1 c. A magnified portion of the surface of one of the articulations of a large individual, showing, in addition to 

 the punctures upon the surface, a series of curving impressed lines. The latter are not observed upon 

 the buckler or caudal shield, which preserves a double series of punctures as shown in PI. 61, fig. 3 c. 



2. A specimen with the crust almost entirely removed. The upper part of the cephalic shield has been se- 

 parated at the mai'ginal suture, leaving tlie lower portion with the epistoma attached as represented in 

 the figure. 



