EXPLANATION OF PLATE 46. 73 



Fig. 11. Anterior segment of the left Eye of Fig. 9, still 

 more highly magnified, to show the circular lenses 

 set in their respective margins, each surrounded by 

 six minute tubercles. (Original.) 



Fig. 11'. Magnified view of a portion of the eye of Caly- 

 mene macrophthalmus. (Hoeninghaus.) 



Fig. 12. Under surface of the anterior portion of the 

 shield of Asaphus platycephalus, from Lake Huron. 

 A unique specimen, showing at/, an entrance to the 

 stomach, analogous to that in recent Crabs. S^e 

 Geol. Trans. N. S. Vol. i. PI. 27. (Stokes.) 



Plate 46. V. I. p. 294 et seq. 



Figs. 1. 2. 3. Calymene Blumenbachii, from the Tran- 

 sition Limestone of Dudley, a. The shield cover- 

 ing the head. a. Lateral portion of the shield, 

 separated by a suture from a.; the central part of 

 this suture forms the lateral Margin, or Rim of the 

 cavity of the Eye. This Margin is composed of 

 two parts, united to receive the Lens, like the rims 

 that enclose the edges of the glasses, in a pair of 

 Spectacles. The Lens has usually fallen out from 

 the Eyes of fossils of this species, as often happens 

 after death in the Eyes of the recent Grapsus pictus, 

 and also in the common Lobster, b. The Eye. c. 

 The dorsal portion, composed of articulating plates, 

 that move on one another like the plates of a Lob- 

 ster's tail. d. The tail. 



Fig. 1. Side view of the animal rolled up like an Oniscus. 

 (Scharf.) 



Fig. 2. View of the back of the Animal expanded for 

 swimming ; the Tail d, is composed of plates that 

 had no movable articulations. (Original.) 



Fig. 3. Front view of the same animal rolled up ; the 



vol. ii. 7 



