PLATE XVIII. 



Fig. 1. — Reniera scotti Kirkp., iiat. size, p. 52. 



Fig. l<a. — Surface, showing pores ( x 2). 



Fig. lb.- — Vertical longitudinal section ( x x). 



Fig. 2. — Reniera scotti, another specimen. 



Fig. ?>. — Reniera dnncoi Topseut, nat. size, p. •'">:!. 



Fig. 4.^ — Petrodafistulata Kirkp., nat. size, p. Ul. 



Fig. 4a.— Surf ace of same ( X 4). 



Fir. 4b.— Section (x 8). 



Fig. .">. — Oceanapia laniula Kirkp., fragments of fistulae, p. 



Fig. .5a. -Closed end of one of the fistulae ( x 4). 



Fig. ijb.— Section (x H). 



