Fig. 2. 
Fig- 1. — PRODUCTA GIGANTEA, ROTUND FORM. 
Fig. 2.— P. (ilGANTEA, ROTUND AND STRONGLY CORRUGATED FORM. 
Fig. 3. — p. COSTATA. 
Proc. Yorks. Geol. Sac, Vol XVI., Plate XXXIX. 
