20 University of Texas Bulletin 



PLATE I 



Fig. 1, Turritella bybeei n. sp., natural size. 



Fig. 2, Turritella bybeei n. sp., X2. 



Fig. 3, Turritella whitneyi n. sp., natural size. 



Fig. 4, Turritella whitneyi n. sp., X5. 



Fig. 5, Turritella washitensis n. sp., natural size. 



Fig. 6, Turritella washitensis n. sp., X2. 



