North American Palaeozoic Crustacea. 



EXPLANATION OF PLATE L 



ILLUSTRATIVE OF THE STRUCTURE OF THE XIPHOSURA AND 



EURYPTERIDA. 



Fig. 1. Belinurus reginse, Bailey ; Coal Measures, Ireland. 



H., Head. Th., Thorax. Ab., Abdomen. T., Telson, 

 Fig. 2. Prestwichia rotundata, Prestwicli ; Coal Measures, Coalbrook Dale, 



Eng. 

 Fig. 3. Hemiaspis limuloides, H. Woodward ; Lower Ludlow shales. 

 Fig. 4. Bunodes limula, Eichw. ; Upper Silurian, Isle of (Esel, Baltic. 

 Fig. 5. Pseudoniscus aculeatus, Nieszk. ; Upper Silurian, Isle of (Esel, Baltic. 

 Fig. 6. Exapinurus Schrenkii, Nieszk. ; Upper Silurian, Isle of OEsel, Baltic. 

 Fig. 7. Eurypterus remipes, De Kay ; Upper Silurian, New York. 



Xote. — The figures given on this plate are copied after those of Dr. Henry 

 Woodward, Proc. Geol. Soc. London, vol. 23, 1867, plate 1. 



EXPLANATION OF PLATE II. 



ILLUSTRATIVE OF THE STRUCTURE OF THE OSTRACODOUS AND 

 PHYLLOPODOUS GENERA. 



[The small horizontal lines indicate the length of the valves when magnified two 

 diameters, for comparison with figs. 17a, h, c] 



Fig.]. Bairdia curta, McCoy. Carboniferous. 1 a. Left valve. 1 ?>, Ventral 

 edge of the same valve. Magnified 15 diam. 



Fig 2. Thlipsuracorpulenta, Jones & HoU. Woolliope beds. Upper Silurian. 

 2 a, Right valve. 2 6, Ventral aspect. 2 c, Posterior extremity. 

 Magnified 15 diam. 



Fig. 3. Cythere Jukesiana, .Jones & Holl. Kildare limestone. Lower Silurian. 

 3 «, Right valve. 3 6, Ventral view. Magnified 15 diam. 



Fig. 4. Cytherella brevis, Jones. Carboniferous, Carluke, Scotland. Magni- 

 fied 15 diam. 



Fig. 5. Cytherellina siliqua, Jones. Upper Silurian. 5 «, Internal cast, with 

 part of the shell, showing level outside and undulated interior. 

 5 6, Right valve. 5 d, End view. Magnified 15 diam. 



Fig. 6. .^chmina cuspidata, Jones & Holl. Wenlock limestone ; Upper Silu- 

 rian. Right valve. Magnified 15 diam. 



Fig. 7. Carbonia Agnes, Jones. Coal Measures, South Wales. 7a, Left valve. 

 76, The internal cast of the muscle-spot and its neighborhood, in 



