EXPLANATION OF PLA'IE XXI. 



Fig-. I. Spiras'trella poculoidcs, sp. nov. ; x 7/10. 



The specimen, which has been longitudinally bi- 

 sected, is viewed from the inner surface. 

 Fig. 2. SpirastreUa alcyonioidcs, sp. nov. ; x 3/5. 

 Fig. 3. SpirastreUa >no}i1il'on}iis, sp. nov. ; x 5/6. 



The surface markings are traces left by an en- 

 crusting Cornulariid Alcyonarian. 



