Plate VI. 



Euplectella oivcni Herkl. & Marsh. 



Fig. 1. A specimen with comparatively prominently developed ledges. 

 7:, nat. size. 



Fig. 2. Upper end of the largest specimen in the Sci. Coll. Miis. seen from 

 the narrower side, '/i "^t- *'''''^- 



Fig. .3. Lower portion of the same specimen, seen from the broader side. 

 -/; nat. size. 



Fig. 4. A specimen (Mr. Owston's) with little ledges or none at all. 7i 

 nat. size. 



Figs. 5-6. Oxyhexasters. 440 x . 



Figs. 7-9. Anchor-head.s of basal spicules. Figs. 7 & 8, abnormally de- 

 veloped. Fig. 9, normal. 1.50 x . 



Fig. 10. Oscularia in situ. To the left, edge of the oscular membrane. 

 100 X. 



