58 



SHELL GALLEKY. 



Case A 1. Section A. Cellularina. — Bvgula turUnata, or the Bird's-head 



Coralline (Fig. 6) grows attached to rocks near low water mark in 

 the form of spiral tufts about two inches in height, composed of 

 narrow flat branches in which the cells are arranged from two to six 

 abreast and all facing upwards. Each cell is boat-shaped and with 



Fig. 6. 



A, Bugula turbinata, natural size. B, portion x 50. 

 a, avicularia ; to, mouth ; o, ovicell. 

 [' The Cambridge Natural History.'] 



nearly the whole front surface membranous ; the globular bodies at 

 the head of certain cells are the ovicells. Attached to the outer edge 

 of each cell is a remarkable object resembling a bird's head, and 

 hence termed avicularium, seated on a short stalk. The head and 

 beak contain powerful muscles for opening and shutting a horny lid 



