EXPLANATION OF PLATES. PPP. 21 



Fig, 12. A fragment of shale preserving the remains of fif- 

 teen young individuals, nine of which are to be 

 seen on the side represented in the figure. 

 Chemung group ; Warren^ Pa. 



ECHINOCARIS PUNCTATA, Holl. 



Page 6. 



Fig. 13 A nearly entire individual showing the form and 

 relation of the i)arts, and the number of naked ab- 

 dominal segments. 



" 14. An enrolled specimen, with the valves partially 

 opened and the abdomen extended along the ven- 

 trum. The specimen shows in a very satisfactory 

 manner the optic spots, the number and distribu- 

 tion of the nodes, and the limits of the cephalic 

 region. 



" 15. id. Lateral view, showing the position of the ab- 

 domen in this example. The specimen is flattened, 

 and does not represent the normal convexity of 

 the valves. 



" 16. The ventral side of a specimen preserving the man- 

 dibles in situ. 

 Hamilton group ; New York. 



PLATE II. 



Elymocaris siliqua, Beecher. 



Page 13. 



Fig. 1. A specimen wanting tlie anterior portion of the 

 carapace, but preserving the abdomen and telson, 

 witli its appendages. 

 '' 2. The carapace with the valves separated, showing 

 their form with the ronnded elevations and optic 

 nodes on the cephalic ])()rtion. 

 Chemung group ; Warren^ Pa. 



