PLATE Y. 
Fig. Pa S e 
1. Ptychoclus rugosus, Dixon; dental crown, coronal and 
lateral aspects.—Chalk; Rochester, Kent. [33249.] 137 
2. Ditto ; tooth, coronal, lateral, and posterior aspects.— 
Chalk; Kent. [33250.] 137 
3. Ditto: upper median tooth, coronal aspect, associated with 
the preceding.—Chalk ; Kent. [33250.] 137 
4-6. Ptychoclus multistriatus, sp. nov.; lower median and 
two lateral teeth, coronal aspect, the anterior margin 
in figs. 4 and 6 inadvertently directed upwards.—Chalk; 
Kent. [P* 2681.] 146 
7. Ptychoclus polygyrus, Agassiz; lower median tooth, coronal 
aspect.—Chalk; near Maidstone. [47905.] 145 
8. Ptychoclus oiveni, Dixon; tooth (?lower median), coronal 
aspect.—II. Chalk; Kent. [39125.] 138 
