SERPULAD^;. 95 



S. intricata. S. serrulata. 



vermicularis. filiformis. 



triquetra. rugosa. 



contortuplicata. Fig. 149 ; n. s. Cordineri. 



Spirorbis (Lamk.). As Serpula, but with only six 

 gill-threads, which are pinnate, retractile and radia- 

 ting. Tube coiled in a flat spiral, cemented to sea- 

 weeds and other submarine substances. 



Dextral. 



S. communis. Fig. 150; mag. * S. incurvatus. 

 spirillum. . pervius. 



granulatus. retortus. 



carinatus. annulus. 



corrugatus. heterocliticus.* 



Montagui. | striatulus. 





Sinistral. 



S. heterostrophus. S. lucidus. 



minutus. reversus. 



Filograna (Berkeley). As Serpula, but with only 

 eight gill-threads, of which two bear a funnel- 

 shaped obliquely-truncate operculum. Tube slender, 

 thread-like, crowded into an irregular mass. 



F. implexa. Fig. 151 ; n. s. 



Ditrupa (Berkl.). Gills of twenty- two threads 

 in two sets, not rolled spirally, singly pinnate. 

 Tube free, open at both ends. 



D. subulata. Fig. 152; mag. -|, 



