PLATE 62. 
Fig. 1, 2. 43. 1. Isotelus gigas. ( Pag. 231.) 
1 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 marginal suture, leaving the lower portion with the epistoma attached as represented in 
the figure. 
