491 



Olen. 



ment of the rock masses; plate 20, fig. 1, smallest specimen of 

 head collected. Note the distance of the eyes from the central head 

 piece (glabella) ; 1 a^ larger specimen, eyes close to glabella, 

 cheek points extended ; 1 5, eyes united to glabella by ridges ; 

 1 /', extreme projection of cheek points. 



Olenellus thompsoni. Hall, (1862, 15th An. Et. p. 114. 



M.C, 



