EXPLANATION OF PLATE II. 



AciDASPis MONSTROSA, Barvaude. 



Figs. 1, 2. Front and profile of a cephalon retaining the detachable cheeks. 

 From Barrande, op. cit,, Supplement, pi. 11, figs. 19, 20. 



ACIDASPIS ROMINGEEI, Hall. 



Figs. 3, 4. Outline figures of the original specimen, copied from Palaeon- 

 tology of New York, vol. vii, pi. 16&, figs. 15, 16. 



