EXPLANATION OF PLATE I. 



Ceratocephala goniata, Warder. 



Fig. 1. Copy of the original figure. From American Journal of Science and 

 Arts, vol. xxxiv, No. *2, p. 378. 



AciDASPis Verneuili, Barrande. 

 Fig. 2. Outline copy of a cephalon viewed from in front as in the preceding 



figure. Barrande, Systeme Silurien du Centre de la Boheme, 



vol. I, pi. 38, fig. 3. 

 Fig. 3. The entire individual. Barrande, loc. cit, fig. 5. 



Trapelocera Hoernesi, Corda. 



Fig. 4. Copy of the original figure. Corda, Prodrome Einer Monographic 

 der bohmischen Trilobiten, pi, vii, fig. 79a. 



DicRANURUs HAMATUS, CoYirad. 



Fig. 5. Copy of the original figure given on the reproduction of the 

 original plate (Fifteenth Kept. N. Y. State Museum), designed to 

 accompany Mr, Conrad's report for 1841. 



Fig. 6. A figure from a cephalon retaining all the parts except the free 

 cheeks. From the trilobitic layers of the Delthyris Shaly lime- 

 stone at Slingerland's, near Clarksville, N. Y. 



Fig. 7. The pygidium and a portion of the thorax as given in Palaeon- 

 tology of New York, vol. iii, pi. 79, fig. 19. 



AciDASPis MONSTROSA, Barrande. 



Fig, 8, A specimen showing a portion of the thorax. From Barrande, 

 op. cit., Suppl. pi. 15, fig. 1. 



AciDASPis Brighti, MurcJiison. 

 Fig. 9. Copy of the original figure in Murchison's Siluria, p. 261, fig. 8. 



