



PLATE XVI A— Continued. 



Hamilton group, Canandaigica, Ontario county. 

 Fig. LP. An individual in a still later, immature stage of growth, enlarged to seven diameters. 



Hamilton group. Hopewell, Ontario county. 

 Pig. 16. A fragment representing the largest pygidium observed. 



Hamilton group. CiinaudaUjim Lake. 

 Fig. IT. Four marginal spines of a pygidium, similar to the one represented iti tig. 9. Enlarged to three 

 diameters. 



Dalmaxites (CkyI'H.EUs) Barrisi. 



Page 4s. 

 Fig. I s \ ]'\ l; - i < 1 i mil. enlarged to three diameter's, and showing the round, terete marginal spines, and the 

 conspicuous terminal spine. 



Hamilton group. Davetuport, Iowa. 



