* The following letters are applied in Pl. 45 and Pl. 46, to corresponding parts
of different animals. a. the shield; a'. lateral portion of the shield ; b. the eye ;
b'. eye magnified ; b". frontal eyes; c. the back; d. the tail; e. branchiæ.

[074]

Figs. l. 2. 3. Calymene Blumenbachii, from the Transition Lime-stone of Dudley. a. The shield covering 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 Lobster's tail. d. The tail.

Fig. l. Side view of the Animal rolled up like an Onis us. (Scharf.)

Fig. 2. View of the back of the Animal expanded for swimming; the Tail d, is composed of plates that had no moveable articulations. (Original.)

Fig. 3. Front view of the same Animal rolled up; the [075] shell, in this position, must have given perfect protection to the soft parts of the body enclosed within. (Scharf.)

Fig. 4. Side view of Calymene macrophthalmus, rolled up, with its tail closed on its shield. (Curtis.)

Fig. 5. Front view of another specimen of C. Macrophthalmus, rolled up like Fig. 4. The Eyes in fossils of this species are usually well preserved, and their facets large. (Curtis.)

Fig. 6. Asaphus tuberculatus; a highly ornamented species from the Transition lime-stone of Dudley; in the collection of Mr. Johnson, of Bristol. The back alone is composed of flexible plates. (Curtis.)

Fig. 7. Asaphus De Buchii, from the Transition slate of Llandilo; the tail is surrounded with an inflexible Margin, slightly fluted. (Brongniart.)

Fig. 8. Restoration of Paradoxoides Tessini, (Brongniart. Hist. Nat. de Crustacés, Pl. IV. Fig. 1.)

Fig. 9. Ogygia Guettardii, (Brongniart, Hist. Nat. de Crustacés, Pl. III. Fig. 1.)

Fig. 10. Highly ornamented tail of Asaphus gemmuliferus, (Phillips), from the Transition lime-stone of Dublin, magnified four times. (Curtis.)

Fig. 11. Tail of Asaphus caudatus, from Carboniferous lime-stone, at Beadnell, Northumberland; in the collection of the Geol. Soc. of London. (Original).

Fig. 12. Tail of Asaphus caudatus, from Tansition [sic] lime-stone, near Leominster; in the Oxford Museum.