PLATE I. 



Pleueoctstites squamosus (page 49). 



Figures la and 16. Dorsal views of two specimens. 



" Ic. Ventral view of a specimen, shewing the plated integument and strong 



borders formed by the folding over of the dorsal plates ; o, the mouth. 

 " Id. Ventral view of the upper part of the cup and arms of a specimen of this 



species, the remainder of which is completely buried in the stone. 

 " le. View of the same, enlarged ; at a is the small sub-apical aperture. It is 



represented too large in the figure. 



Pleueocystites eobustus (page 49). 



Figure 2a shews a fragment of the upper part of a specimen. From the position in 

 which the artist viewed the specimen, the left rhomb in the figure appears 

 too angular on the upper side. 



Pleueoctstites Anticostiensis (page 52), 



Figure 3. Dorsal view of an imperfect specimen of this species. 



