PLATE X. 



FIG. 1. Obotus lens. a, ventral valve b, interior of same, c, longitudinal section of 

 same, d, dorsal valve, c, interior of same,/, longitudinal section of same. 

 All Mag. j , except fig. 1 b, which is enlarged 2 T S . All from Assise E. 3 e at 

 Dugald brook, Escasonie. See p. 144. 

 0. lens, var. lorn/us, n. var. See pi. vii, fig. 4. See p. 140. 



FIG. 2. BillimjscUa retroflexa a, mould of ventral valve b, another mould narrowed 

 by pressure, showing vascular trunks c, mould of the dorsal valve d, mould 

 of the exterior of the dorsal c, longitudinal section of both valves. All Mag. 

 f. From Assise E. 2 (a?) Young point, George river, Escasonie, N. S. 

 See p. 148. 



FIG. 3. Holasaphus ccntropyyc. a middle piece of the head shield ; b Pygidium ; c 

 Movable cheek. All Mag. -?-. From Assise E 2 (a?) at Young point, George 

 river, N. S. See p. 174. 



